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	$134.72	7.268%	$144.5114	$144.51	$144.50	$144.50
Purchase #2	$227.45	7.475%	$244.4519	$244.45	$244.45	$244.50
Purchase #3	$228.53	12.379%	$256.8197	$256.82	$256.80	$256.80
Purchase #4	$151.99	6.648%	$162.0943	$162.09	$162.10	$162.10
Purchase #5	$156.61	13.117%	$177.1525	$177.15	$177.15	$177.20
Purchase #6	$72.98	13.121%	$82.5557	$82.56	$82.55	$82.60
Purchase #7	$45.94	9.440%	$50.2767	$50.28	$50.30	$50.30
7 purchase totals =	$1,018.22		$1,117.8622	$1,117.86	$1,117.85	$1,118.00