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	$226.72	13.282%	$256.833	$256.83	$256.85	$256.80
Purchase #2	$72.40	11.280%	$80.5667	$80.57	$80.55	$80.60
Purchase #3	$151.48	13.654%	$172.1631	$172.16	$172.15	$172.20
Purchase #4	$230.71	4.761%	$241.6941	$241.69	$241.70	$241.70
Purchase #5	$73.39	6.499%	$78.1596	$78.16	$78.15	$78.20
Purchase #6	$234.57	12.848%	$264.7076	$264.71	$264.70	$264.70
Purchase #7	$108.38	13.285%	$122.7783	$122.78	$122.80	$122.80
7 purchase totals =	$1,097.65		$1,216.9024	$1,216.90	$1,216.90	$1,217.00