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	$80.83	6.315%	$85.9344	$85.93	$85.95	$85.90
Purchase #2	$126.55	10.529%	$139.8744	$139.87	$139.85	$139.90
Purchase #3	$190.30	4.605%	$199.0633	$199.06	$199.05	$199.10
Purchase #4	$170.38	13.681%	$193.6897	$193.69	$193.70	$193.70
Purchase #5	$31.32	6.553%	$33.3724	$33.37	$33.35	$33.40
Purchase #6	$10.34	5.146%	$10.8721	$10.87	$10.85	$10.90
Purchase #7	$92.45	8.698%	$100.4913	$100.49	$100.50	$100.50
7 purchase totals =	$702.17		$763.2976	$763.28	$763.25	$763.40