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	$10.50	4.105%	$10.931	$10.93	$10.95	$10.90
Purchase #2	$208.38	13.193%	$235.8716	$235.87	$235.85	$235.90
Purchase #3	$41.69	10.650%	$46.13	$46.13	$46.15	$46.10
Purchase #4	$56.47	5.199%	$59.4059	$59.41	$59.40	$59.40
Purchase #5	$88.65	9.265%	$96.8634	$96.86	$96.85	$96.90
Purchase #6	$121.64	12.851%	$137.272	$137.27	$137.25	$137.30
Purchase #7	$50.57	4.579%	$52.8856	$52.89	$52.90	$52.90
7 purchase totals =	$577.90		$639.3595	$639.36	$639.35	$639.40