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	$55.89	8.708%	$60.7569	$60.76	$60.75	$60.80
Purchase #2	$139.65	9.164%	$152.4475	$152.45	$152.45	$152.40
Purchase #3	$97.40	12.697%	$109.7669	$109.77	$109.75	$109.80
Purchase #4	$55.71	11.408%	$62.0654	$62.07	$62.05	$62.10
Purchase #5	$32.73	13.782%	$37.2408	$37.24	$37.25	$37.20
Purchase #6	$89.30	11.429%	$99.5061	$99.51	$99.50	$99.50
Purchase #7	$221.35	11.688%	$247.2214	$247.22	$247.20	$247.20
7 purchase totals =	$692.03		$769.0050	$769.02	$768.95	$769.00