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	$199.72	11.520%	$222.7277	$222.73	$222.75	$222.70
Purchase #2	$208.46	9.491%	$228.2449	$228.24	$228.25	$228.20
Purchase #3	$28.29	11.633%	$31.581	$31.58	$31.60	$31.60
Purchase #4	$120.46	8.494%	$130.6919	$130.69	$130.70	$130.70
Purchase #5	$133.33	7.532%	$143.3724	$143.37	$143.35	$143.40
Purchase #6	$128.44	3.806%	$133.3284	$133.33	$133.35	$133.30
Purchase #7	$152.31	8.519%	$165.2853	$165.29	$165.30	$165.30
7 purchase totals =	$971.01		$1,055.2316	$1,055.23	$1,055.30	$1,055.20