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	$146.59	4.423%	$153.0737	$153.07	$153.05	$153.10
Purchase #2	$83.73	8.502%	$90.8487	$90.85	$90.85	$90.80
Purchase #3	$13.96	8.477%	$15.1434	$15.14	$15.15	$15.10
Purchase #4	$151.72	13.724%	$172.5421	$172.54	$172.55	$172.50
Purchase #5	$110.43	12.495%	$124.2282	$124.23	$124.25	$124.20
Purchase #6	$47.60	12.418%	$53.511	$53.51	$53.50	$53.50
Purchase #7	$26.39	7.211%	$28.293	$28.29	$28.30	$28.30
7 purchase totals =	$580.42		$637.6401	$637.63	$637.65	$637.50