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	$76.86	8.180%	$83.1471	$83.15	$83.15	$83.10
Purchase #2	$170.61	13.795%	$194.1456	$194.15	$194.15	$194.10
Purchase #3	$29.91	8.594%	$32.4805	$32.48	$32.50	$32.50
Purchase #4	$137.58	8.141%	$148.7804	$148.78	$148.80	$148.80
Purchase #5	$33.45	5.582%	$35.3172	$35.32	$35.30	$35.30
Purchase #6	$134.94	11.680%	$150.701	$150.70	$150.70	$150.70
Purchase #7	$30.27	7.587%	$32.5666	$32.57	$32.55	$32.60
7 purchase totals =	$613.62		$677.1384	$677.15	$677.15	$677.10