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	$71.75	11.426%	$79.9482	$79.95	$79.95	$79.90
Purchase #2	$244.58	4.758%	$256.2171	$256.22	$256.20	$256.20
Purchase #3	$199.98	12.207%	$224.3916	$224.39	$224.40	$224.40
Purchase #4	$69.34	3.419%	$71.7107	$71.71	$71.70	$71.70
Purchase #5	$136.97	6.725%	$146.1812	$146.18	$146.20	$146.20
Purchase #6	$135.37	11.183%	$150.5084	$150.51	$150.50	$150.50
Purchase #7	$213.29	4.386%	$222.6449	$222.64	$222.65	$222.60
7 purchase totals =	$1,071.28		$1,151.6021	$1,151.60	$1,151.60	$1,151.50