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	$141.40	3.573%	$146.4522	$146.45	$146.45	$146.50
Purchase #2	$212.42	13.873%	$241.889	$241.89	$241.90	$241.90
Purchase #3	$62.43	3.347%	$64.5195	$64.52	$64.50	$64.50
Purchase #4	$204.44	11.301%	$227.5438	$227.54	$227.55	$227.50
Purchase #5	$99.33	12.263%	$111.5108	$111.51	$111.50	$111.50
Purchase #6	$30.46	5.639%	$32.1776	$32.18	$32.20	$32.20
Purchase #7	$201.98	5.554%	$213.198	$213.20	$213.20	$213.20
7 purchase totals =	$952.46		$1,037.2909	$1,037.29	$1,037.30	$1,037.30