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	$165.69	13.555%	$188.1493	$188.15	$188.15	$188.10
Purchase #2	$163.57	7.217%	$175.3748	$175.37	$175.35	$175.40
Purchase #3	$124.77	9.558%	$136.6955	$136.70	$136.70	$136.70
Purchase #4	$38.88	3.801%	$40.3578	$40.36	$40.35	$40.40
Purchase #5	$230.68	13.113%	$260.9291	$260.93	$260.95	$260.90
Purchase #6	$173.76	10.872%	$192.6512	$192.65	$192.65	$192.70
Purchase #7	$59.65	12.742%	$67.2506	$67.25	$67.25	$67.30
7 purchase totals =	$957.00		$1,061.4083	$1,061.41	$1,061.40	$1,061.50