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	$135.75	7.309%	$145.672	$145.67	$145.65	$145.70
Purchase #2	$133.54	11.503%	$148.9011	$148.90	$148.90	$148.90
Purchase #3	$228.72	10.403%	$252.5137	$252.51	$252.50	$252.50
Purchase #4	$196.43	4.478%	$205.2261	$205.23	$205.25	$205.20
Purchase #5	$79.29	3.689%	$82.215	$82.22	$82.20	$82.20
Purchase #6	$155.89	11.196%	$173.3434	$173.34	$173.35	$173.30
Purchase #7	$84.95	4.250%	$88.5604	$88.56	$88.55	$88.60
7 purchase totals =	$1,014.57		$1,096.4317	$1,096.43	$1,096.40	$1,096.40