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	$87.45	13.243%	$99.031	$99.03	$99.05	$99.00
Purchase #2	$110.31	12.108%	$123.6663	$123.67	$123.65	$123.70
Purchase #3	$120.26	10.105%	$132.4123	$132.41	$132.40	$132.40
Purchase #4	$150.87	7.715%	$162.5096	$162.51	$162.50	$162.50
Purchase #5	$232.76	8.178%	$251.7951	$251.80	$251.80	$251.80
Purchase #6	$131.63	7.327%	$141.2745	$141.27	$141.25	$141.30
Purchase #7	$135.78	12.344%	$152.5407	$152.54	$152.55	$152.50
7 purchase totals =	$969.06		$1,063.2295	$1,063.23	$1,063.20	$1,063.20