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	$153.57	7.330%	$164.8267	$164.83	$164.85	$164.80
Purchase #2	$89.62	4.755%	$93.8814	$93.88	$93.90	$93.90
Purchase #3	$185.72	6.439%	$197.6785	$197.68	$197.70	$197.70
Purchase #4	$141.81	6.593%	$151.1595	$151.16	$151.15	$151.20
Purchase #5	$10.79	12.566%	$12.1459	$12.15	$12.15	$12.10
Purchase #6	$25.39	12.141%	$28.4726	$28.47	$28.45	$28.50
Purchase #7	$151.62	13.746%	$172.4617	$172.46	$172.45	$172.50
7 purchase totals =	$758.52		$820.6263	$820.63	$820.65	$820.70