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	$93.89	10.668%	$103.9062	$103.91	$103.90	$103.90
Purchase #2	$66.32	11.739%	$74.1053	$74.11	$74.10	$74.10
Purchase #3	$242.69	5.768%	$256.6884	$256.69	$256.70	$256.70
Purchase #4	$217.56	12.485%	$244.7224	$244.72	$244.70	$244.70
Purchase #5	$61.37	4.109%	$63.8917	$63.89	$63.90	$63.90
Purchase #6	$227.63	6.464%	$242.344	$242.34	$242.35	$242.30
Purchase #7	$55.31	11.750%	$61.8089	$61.81	$61.80	$61.80
7 purchase totals =	$964.77		$1,047.4669	$1,047.47	$1,047.45	$1,047.40