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	$144.27	6.150%	$153.1426	$153.14	$153.15	$153.10
Purchase #2	$161.99	6.864%	$173.109	$173.11	$173.10	$173.10
Purchase #3	$44.47	4.338%	$46.3991	$46.40	$46.40	$46.40
Purchase #4	$232.81	12.248%	$261.3246	$261.32	$261.30	$261.30
Purchase #5	$58.89	9.677%	$64.5888	$64.59	$64.60	$64.60
Purchase #6	$143.56	5.742%	$151.8032	$151.80	$151.80	$151.80
Purchase #7	$222.61	13.801%	$253.3324	$253.33	$253.35	$253.30
7 purchase totals =	$1,008.60		$1,103.6997	$1,103.69	$1,103.70	$1,103.60