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	$61.96	4.733%	$64.8926	$64.89	$64.90	$64.90
Purchase #2	$44.75	8.414%	$48.5153	$48.52	$48.50	$48.50
Purchase #3	$190.90	3.155%	$196.9229	$196.92	$196.90	$196.90
Purchase #4	$128.48	12.381%	$144.3871	$144.39	$144.40	$144.40
Purchase #5	$215.35	12.640%	$242.5702	$242.57	$242.55	$242.60
Purchase #6	$124.58	6.275%	$132.3974	$132.40	$132.40	$132.40
Purchase #7	$23.47	6.615%	$25.0225	$25.02	$25.00	$25.00
7 purchase totals =	$789.49		$854.7080	$854.71	$854.65	$854.70