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	$91.32	4.522%	$95.4495	$95.45	$95.45	$95.40
Purchase #2	$65.79	13.143%	$74.4368	$74.44	$74.45	$74.40
Purchase #3	$138.73	12.512%	$156.0879	$156.09	$156.10	$156.10
Purchase #4	$99.51	3.570%	$103.0625	$103.06	$103.05	$103.10
Purchase #5	$33.77	7.833%	$36.4152	$36.42	$36.40	$36.40
Purchase #6	$95.58	13.331%	$108.3218	$108.32	$108.30	$108.30
Purchase #7	$29.89	11.536%	$33.3381	$33.34	$33.35	$33.30
7 purchase totals =	$554.59		$607.1118	$607.12	$607.10	$607.00