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	$28.60	13.524%	$32.4679	$32.47	$32.45	$32.50
Purchase #2	$29.47	13.703%	$33.5083	$33.51	$33.50	$33.50
Purchase #3	$151.67	5.374%	$159.8207	$159.82	$159.80	$159.80
Purchase #4	$24.54	6.460%	$26.1253	$26.13	$26.15	$26.10
Purchase #5	$147.62	3.642%	$152.9963	$153.00	$153.00	$153.00
Purchase #6	$146.46	7.522%	$157.4767	$157.48	$157.50	$157.50
Purchase #7	$97.77	7.254%	$104.8622	$104.86	$104.85	$104.90
7 purchase totals =	$626.13		$667.2574	$667.27	$667.25	$667.30