Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$214.40	5.193%	$225.5338	$225.53	$225.55	$225.50
Purchase #2	$188.40	6.592%	$200.8193	$200.82	$200.80	$200.80
Purchase #3	$244.97	12.414%	$275.3806	$275.38	$275.40	$275.40
Purchase #4	$183.42	6.537%	$195.4102	$195.41	$195.40	$195.40
Purchase #5	$99.32	9.870%	$109.1229	$109.12	$109.10	$109.10
Purchase #6	$47.92	9.753%	$52.5936	$52.59	$52.60	$52.60
Purchase #7	$205.69	12.169%	$230.7204	$230.72	$230.70	$230.70
7 purchase totals =	$1,184.12		$1,289.5808	$1,289.57	$1,289.55	$1,289.50