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	$28.74	11.625%	$32.081	$32.08	$32.10	$32.10
Purchase #2	$74.73	9.650%	$81.9414	$81.94	$81.95	$81.90
Purchase #3	$43.67	10.723%	$48.3527	$48.35	$48.35	$48.40
Purchase #4	$66.47	9.747%	$72.9488	$72.95	$72.95	$72.90
Purchase #5	$168.39	4.114%	$175.3176	$175.32	$175.30	$175.30
Purchase #6	$74.30	10.509%	$82.1082	$82.11	$82.10	$82.10
Purchase #7	$249.26	10.348%	$275.0534	$275.05	$275.05	$275.10
7 purchase totals =	$705.56		$767.8031	$767.80	$767.80	$767.80