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	$222.71	7.559%	$239.5446	$239.54	$239.55	$239.50
Purchase #2	$182.81	12.749%	$206.1164	$206.12	$206.10	$206.10
Purchase #3	$166.79	5.867%	$176.5756	$176.58	$176.60	$176.60
Purchase #4	$127.29	13.703%	$144.7325	$144.73	$144.75	$144.70
Purchase #5	$204.60	4.191%	$213.1748	$213.17	$213.15	$213.20
Purchase #6	$143.30	5.561%	$151.2689	$151.27	$151.25	$151.30
Purchase #7	$102.53	8.731%	$111.4819	$111.48	$111.50	$111.50
7 purchase totals =	$1,150.03		$1,242.8947	$1,242.89	$1,242.90	$1,242.90