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	$140.91	10.316%	$155.4463	$155.45	$155.45	$155.40
Purchase #2	$44.94	12.491%	$50.5535	$50.55	$50.55	$50.60
Purchase #3	$202.77	5.504%	$213.9305	$213.93	$213.95	$213.90
Purchase #4	$224.55	7.228%	$240.7805	$240.78	$240.80	$240.80
Purchase #5	$225.40	9.793%	$247.4734	$247.47	$247.45	$247.50
Purchase #6	$157.40	3.105%	$162.2873	$162.29	$162.30	$162.30
Purchase #7	$78.45	5.160%	$82.498	$82.50	$82.50	$82.50
7 purchase totals =	$1,074.42		$1,152.9695	$1,152.97	$1,153.00	$1,153.00