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	$144.81	4.697%	$151.6117	$151.61	$151.60	$151.60
Purchase #2	$224.43	4.238%	$233.9413	$233.94	$233.95	$233.90
Purchase #3	$101.43	10.206%	$111.7819	$111.78	$111.80	$111.80
Purchase #4	$17.26	4.309%	$18.0037	$18.00	$18.00	$18.00
Purchase #5	$33.96	5.475%	$35.8193	$35.82	$35.80	$35.80
Purchase #6	$107.33	7.874%	$115.7812	$115.78	$115.80	$115.80
Purchase #7	$233.44	11.851%	$261.105	$261.11	$261.10	$261.10
7 purchase totals =	$862.66		$928.0441	$928.04	$928.05	$928.00