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	$194.50	13.813%	$221.3663	$221.37	$221.35	$221.40
Purchase #2	$51.66	12.602%	$58.1702	$58.17	$58.15	$58.20
Purchase #3	$235.37	11.366%	$262.1222	$262.12	$262.10	$262.10
Purchase #4	$80.83	11.678%	$90.2693	$90.27	$90.25	$90.30
Purchase #5	$196.51	10.713%	$217.5621	$217.56	$217.55	$217.60
Purchase #6	$199.57	4.562%	$208.6744	$208.67	$208.65	$208.70
Purchase #7	$213.86	6.216%	$227.1535	$227.15	$227.15	$227.20
7 purchase totals =	$1,172.30		$1,285.3180	$1,285.31	$1,285.20	$1,285.50