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	$106.28	5.276%	$111.8873	$111.89	$111.90	$111.90
Purchase #2	$59.30	3.619%	$61.4461	$61.45	$61.45	$61.40
Purchase #3	$169.75	12.275%	$190.5868	$190.59	$190.60	$190.60
Purchase #4	$235.50	6.445%	$250.678	$250.68	$250.70	$250.70
Purchase #5	$29.88	8.317%	$32.3651	$32.37	$32.35	$32.40
Purchase #6	$60.49	8.546%	$65.6595	$65.66	$65.65	$65.70
Purchase #7	$55.91	11.390%	$62.2781	$62.28	$62.30	$62.30
7 purchase totals =	$717.11		$774.9009	$774.92	$774.95	$775.00