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	$40.25	13.612%	$45.7288	$45.73	$45.75	$45.70
Purchase #2	$212.53	9.113%	$231.8979	$231.90	$231.90	$231.90
Purchase #3	$199.28	10.211%	$219.6285	$219.63	$219.65	$219.60
Purchase #4	$225.33	10.363%	$248.6809	$248.68	$248.70	$248.70
Purchase #5	$223.53	4.842%	$234.3533	$234.35	$234.35	$234.40
Purchase #6	$94.47	5.834%	$99.9814	$99.98	$100.00	$100.00
Purchase #7	$69.89	3.141%	$72.0852	$72.09	$72.10	$72.10
7 purchase totals =	$1,065.28		$1,152.3560	$1,152.36	$1,152.45	$1,152.40