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	$206.70	5.788%	$218.6638	$218.66	$218.65	$218.70
Purchase #2	$233.86	13.115%	$264.5307	$264.53	$264.55	$264.50
Purchase #3	$215.53	8.389%	$233.6108	$233.61	$233.60	$233.60
Purchase #4	$81.65	4.784%	$85.5561	$85.56	$85.55	$85.60
Purchase #5	$223.73	5.113%	$235.1693	$235.17	$235.15	$235.20
Purchase #6	$195.51	7.855%	$210.8673	$210.87	$210.85	$210.90
Purchase #7	$243.83	7.800%	$262.8487	$262.85	$262.85	$262.80
7 purchase totals =	$1,400.81		$1,511.2467	$1,511.25	$1,511.20	$1,511.30