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	$110.32	13.477%	$125.1878	$125.19	$125.20	$125.20
Purchase #2	$155.44	6.594%	$165.6897	$165.69	$165.70	$165.70
Purchase #3	$74.41	5.596%	$78.574	$78.57	$78.55	$78.60
Purchase #4	$119.48	9.857%	$131.2571	$131.26	$131.25	$131.30
Purchase #5	$175.46	9.650%	$192.3919	$192.39	$192.40	$192.40
Purchase #6	$145.69	9.162%	$159.0381	$159.04	$159.05	$159.00
Purchase #7	$41.43	3.592%	$42.9182	$42.92	$42.90	$42.90
7 purchase totals =	$822.23		$895.0568	$895.06	$895.05	$895.10