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	$204.54	9.166%	$223.2881	$223.29	$223.30	$223.30
Purchase #2	$198.61	10.740%	$219.9407	$219.94	$219.95	$219.90
Purchase #3	$77.26	10.257%	$85.1846	$85.18	$85.20	$85.20
Purchase #4	$35.47	5.580%	$37.4492	$37.45	$37.45	$37.40
Purchase #5	$214.85	5.717%	$227.133	$227.13	$227.15	$227.10
Purchase #6	$223.59	13.780%	$254.4007	$254.40	$254.40	$254.40
Purchase #7	$158.59	6.144%	$168.3338	$168.33	$168.35	$168.30
7 purchase totals =	$1,112.91		$1,215.7301	$1,215.72	$1,215.80	$1,215.60