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	$118.27	4.460%	$123.5448	$123.54	$123.55	$123.50
Purchase #2	$56.45	5.848%	$59.7512	$59.75	$59.75	$59.80
Purchase #3	$122.55	11.679%	$136.8626	$136.86	$136.85	$136.90
Purchase #4	$210.35	13.217%	$238.152	$238.15	$238.15	$238.20
Purchase #5	$56.66	7.848%	$61.1067	$61.11	$61.10	$61.10
Purchase #6	$69.30	13.171%	$78.4275	$78.43	$78.45	$78.40
Purchase #7	$38.30	10.406%	$42.2855	$42.29	$42.30	$42.30
7 purchase totals =	$671.88		$740.1303	$740.13	$740.15	$740.20