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	$50.25	8.209%	$54.375	$54.38	$54.40	$54.40
Purchase #2	$222.66	4.452%	$232.5728	$232.57	$232.55	$232.60
Purchase #3	$90.81	7.738%	$97.8369	$97.84	$97.85	$97.80
Purchase #4	$55.27	3.740%	$57.3371	$57.34	$57.35	$57.30
Purchase #5	$59.35	3.322%	$61.3216	$61.32	$61.30	$61.30
Purchase #6	$130.80	13.717%	$148.7418	$148.74	$148.75	$148.70
Purchase #7	$103.52	7.690%	$111.4807	$111.48	$111.50	$111.50
7 purchase totals =	$712.66		$763.6659	$763.67	$763.70	$763.60