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	$143.74	12.625%	$161.8872	$161.89	$161.90	$161.90
Purchase #2	$210.82	5.426%	$222.2591	$222.26	$222.25	$222.30
Purchase #3	$88.30	12.418%	$99.2651	$99.27	$99.25	$99.30
Purchase #4	$29.68	10.527%	$32.8044	$32.80	$32.80	$32.80
Purchase #5	$55.34	7.513%	$59.4977	$59.50	$59.50	$59.50
Purchase #6	$158.57	12.248%	$177.9917	$177.99	$178.00	$178.00
Purchase #7	$57.38	7.405%	$61.629	$61.63	$61.65	$61.60
7 purchase totals =	$743.83		$815.3342	$815.34	$815.35	$815.40