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	$199.61	7.144%	$213.8701	$213.87	$213.85	$213.90
Purchase #2	$82.34	7.343%	$88.3862	$88.39	$88.40	$88.40
Purchase #3	$214.35	3.609%	$222.0859	$222.09	$222.10	$222.10
Purchase #4	$34.41	9.250%	$37.5929	$37.59	$37.60	$37.60
Purchase #5	$136.74	8.813%	$148.7909	$148.79	$148.80	$148.80
Purchase #6	$224.84	11.130%	$249.8647	$249.86	$249.85	$249.90
Purchase #7	$110.65	12.759%	$124.7678	$124.77	$124.75	$124.80
7 purchase totals =	$1,002.94		$1,085.3585	$1,085.36	$1,085.35	$1,085.50