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	$129.73	9.182%	$141.6418	$141.64	$141.65	$141.60
Purchase #2	$128.82	12.281%	$144.6404	$144.64	$144.65	$144.60
Purchase #3	$175.47	8.616%	$190.5885	$190.59	$190.60	$190.60
Purchase #4	$55.51	9.800%	$60.95	$60.95	$60.95	$61.00
Purchase #5	$215.29	10.767%	$238.4703	$238.47	$238.45	$238.50
Purchase #6	$196.96	11.654%	$219.9137	$219.91	$219.90	$219.90
Purchase #7	$18.56	10.428%	$20.4954	$20.50	$20.50	$20.50
7 purchase totals =	$920.34		$1,016.7001	$1,016.70	$1,016.70	$1,016.70