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	$188.93	4.222%	$196.9066	$196.91	$196.90	$196.90
Purchase #2	$44.81	5.186%	$47.1338	$47.13	$47.15	$47.10
Purchase #3	$134.60	8.672%	$146.2725	$146.27	$146.25	$146.30
Purchase #4	$176.67	4.528%	$184.6696	$184.67	$184.65	$184.70
Purchase #5	$245.28	13.708%	$278.903	$278.90	$278.90	$278.90
Purchase #6	$76.33	4.522%	$79.7816	$79.78	$79.80	$79.80
Purchase #7	$88.69	12.195%	$99.5057	$99.51	$99.50	$99.50
7 purchase totals =	$955.31		$1,033.1728	$1,033.17	$1,033.15	$1,033.20