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	$223.48	11.302%	$248.7377	$248.74	$248.75	$248.70
Purchase #2	$134.53	8.319%	$145.7216	$145.72	$145.70	$145.70
Purchase #3	$218.93	6.608%	$233.3969	$233.40	$233.40	$233.40
Purchase #4	$52.66	7.456%	$56.5863	$56.59	$56.60	$56.60
Purchase #5	$97.67	5.195%	$102.744	$102.74	$102.75	$102.70
Purchase #6	$34.90	10.154%	$38.4437	$38.44	$38.45	$38.40
Purchase #7	$246.73	4.119%	$256.8928	$256.89	$256.90	$256.90
7 purchase totals =	$1,008.90		$1,082.5230	$1,082.52	$1,082.55	$1,082.40