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	$54.32	7.635%	$58.4673	$58.47	$58.45	$58.50
Purchase #2	$137.91	9.766%	$151.3783	$151.38	$151.40	$151.40
Purchase #3	$169.72	8.590%	$184.2989	$184.30	$184.30	$184.30
Purchase #4	$149.99	11.223%	$166.8234	$166.82	$166.80	$166.80
Purchase #5	$56.87	8.867%	$61.9127	$61.91	$61.90	$61.90
Purchase #6	$221.42	11.810%	$247.5697	$247.57	$247.55	$247.60
Purchase #7	$98.30	13.629%	$111.6973	$111.70	$111.70	$111.70
7 purchase totals =	$888.53		$982.1476	$982.15	$982.10	$982.20