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	$207.47	9.595%	$227.3767	$227.38	$227.40	$227.40
Purchase #2	$135.26	9.437%	$148.0245	$148.02	$148.00	$148.00
Purchase #3	$44.71	7.611%	$48.1129	$48.11	$48.10	$48.10
Purchase #4	$230.89	10.837%	$255.9115	$255.91	$255.90	$255.90
Purchase #5	$244.28	12.706%	$275.3182	$275.32	$275.30	$275.30
Purchase #6	$78.58	4.470%	$82.0925	$82.09	$82.10	$82.10
Purchase #7	$50.85	9.869%	$55.8684	$55.87	$55.85	$55.90
7 purchase totals =	$992.04		$1,092.7047	$1,092.70	$1,092.65	$1,092.70