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	$42.74	6.149%	$45.3681	$45.37	$45.35	$45.40
Purchase #2	$192.79	6.689%	$205.6857	$205.69	$205.70	$205.70
Purchase #3	$145.56	7.229%	$156.0825	$156.08	$156.10	$156.10
Purchase #4	$203.25	5.618%	$214.6686	$214.67	$214.65	$214.70
Purchase #5	$32.40	3.798%	$33.6306	$33.63	$33.65	$33.60
Purchase #6	$184.95	3.197%	$190.8629	$190.86	$190.85	$190.90
Purchase #7	$146.32	7.510%	$157.3086	$157.31	$157.30	$157.30
7 purchase totals =	$948.01		$1,003.6070	$1,003.61	$1,003.60	$1,003.70