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	$228.26	10.357%	$251.9009	$251.90	$251.90	$251.90
Purchase #2	$169.78	13.548%	$192.7818	$192.78	$192.80	$192.80
Purchase #3	$118.43	7.448%	$127.2507	$127.25	$127.25	$127.30
Purchase #4	$155.34	3.370%	$160.575	$160.58	$160.60	$160.60
Purchase #5	$77.60	7.698%	$83.5736	$83.57	$83.55	$83.60
Purchase #6	$213.51	3.318%	$220.5943	$220.59	$220.60	$220.60
Purchase #7	$189.97	9.726%	$208.4465	$208.45	$208.45	$208.40
7 purchase totals =	$1,152.89		$1,245.1228	$1,245.12	$1,245.15	$1,245.20