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	$137.48	4.672%	$143.9031	$143.90	$143.90	$143.90
Purchase #2	$26.52	4.326%	$27.6673	$27.67	$27.65	$27.70
Purchase #3	$19.54	11.744%	$21.8348	$21.83	$21.85	$21.80
Purchase #4	$9.64	9.621%	$10.5675	$10.57	$10.55	$10.60
Purchase #5	$217.47	12.331%	$244.2862	$244.29	$244.30	$244.30
Purchase #6	$33.65	7.675%	$36.2326	$36.23	$36.25	$36.20
Purchase #7	$54.72	13.113%	$61.8954	$61.90	$61.90	$61.90
7 purchase totals =	$499.02		$546.3869	$546.39	$546.40	$546.40