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	$169.90	12.257%	$190.7246	$190.72	$190.70	$190.70
Purchase #2	$46.96	13.626%	$53.3588	$53.36	$53.35	$53.40
Purchase #3	$82.62	11.122%	$91.809	$91.81	$91.80	$91.80
Purchase #4	$10.69	12.735%	$12.0514	$12.05	$12.05	$12.10
Purchase #5	$201.56	13.208%	$228.182	$228.18	$228.20	$228.20
Purchase #6	$84.92	5.853%	$89.8904	$89.89	$89.90	$89.90
Purchase #7	$225.39	7.121%	$241.44	$241.44	$241.45	$241.40
7 purchase totals =	$822.04		$907.4562	$907.45	$907.45	$907.50