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	$100.33	9.764%	$110.1262	$110.13	$110.15	$110.10
Purchase #2	$66.41	9.427%	$72.6705	$72.67	$72.65	$72.70
Purchase #3	$168.49	13.445%	$191.1435	$191.14	$191.15	$191.10
Purchase #4	$177.46	4.494%	$185.4351	$185.44	$185.45	$185.40
Purchase #5	$65.41	7.563%	$70.357	$70.36	$70.35	$70.40
Purchase #6	$159.93	11.733%	$178.6946	$178.69	$178.70	$178.70
Purchase #7	$135.56	6.833%	$144.8228	$144.82	$144.80	$144.80
7 purchase totals =	$873.59		$953.2497	$953.25	$953.25	$953.20