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	$236.92	4.582%	$247.7757	$247.78	$247.80	$247.80
Purchase #2	$147.45	4.173%	$153.6031	$153.60	$153.60	$153.60
Purchase #3	$98.47	11.403%	$109.6985	$109.70	$109.70	$109.70
Purchase #4	$230.50	11.431%	$256.8485	$256.85	$256.85	$256.80
Purchase #5	$13.45	4.593%	$14.0678	$14.07	$14.05	$14.10
Purchase #6	$152.89	4.684%	$160.0514	$160.05	$160.05	$160.10
Purchase #7	$77.78	13.785%	$88.502	$88.50	$88.50	$88.50
7 purchase totals =	$957.46		$1,030.5470	$1,030.55	$1,030.55	$1,030.60