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	$108.47	4.593%	$113.452	$113.45	$113.45	$113.50
Purchase #2	$18.81	13.622%	$21.3723	$21.37	$21.35	$21.40
Purchase #3	$55.88	7.874%	$60.28	$60.28	$60.30	$60.30
Purchase #4	$196.68	6.453%	$209.3718	$209.37	$209.35	$209.40
Purchase #5	$31.76	4.347%	$33.1406	$33.14	$33.15	$33.10
Purchase #6	$156.91	8.485%	$170.2238	$170.22	$170.20	$170.20
Purchase #7	$96.53	9.258%	$105.4667	$105.47	$105.45	$105.50
7 purchase totals =	$665.04		$713.3072	$713.30	$713.25	$713.40