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	$54.39	7.213%	$58.3132	$58.31	$58.30	$58.30
Purchase #2	$20.31	9.546%	$22.2488	$22.25	$22.25	$22.20
Purchase #3	$133.98	13.238%	$151.7163	$151.72	$151.70	$151.70
Purchase #4	$148.89	9.231%	$162.634	$162.63	$162.65	$162.60
Purchase #5	$57.83	3.559%	$59.8882	$59.89	$59.90	$59.90
Purchase #6	$124.33	12.378%	$139.7196	$139.72	$139.70	$139.70
Purchase #7	$211.54	9.576%	$231.7971	$231.80	$231.80	$231.80
7 purchase totals =	$751.27		$826.3172	$826.32	$826.30	$826.20