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	$149.43	10.505%	$165.1276	$165.13	$165.15	$165.10
Purchase #2	$74.42	11.766%	$83.1763	$83.18	$83.20	$83.20
Purchase #3	$212.65	3.706%	$220.5308	$220.53	$220.55	$220.50
Purchase #4	$219.37	11.864%	$245.3961	$245.40	$245.40	$245.40
Purchase #5	$18.84	7.379%	$20.2302	$20.23	$20.25	$20.20
Purchase #6	$38.80	12.407%	$43.6139	$43.61	$43.60	$43.60
Purchase #7	$140.43	7.157%	$150.4806	$150.48	$150.50	$150.50
7 purchase totals =	$853.94		$928.5555	$928.56	$928.65	$928.50