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	$182.68	3.420%	$188.9277	$188.93	$188.95	$188.90
Purchase #2	$221.42	5.541%	$233.6889	$233.69	$233.70	$233.70
Purchase #3	$175.31	13.819%	$199.5361	$199.54	$199.55	$199.50
Purchase #4	$75.50	10.277%	$83.2591	$83.26	$83.25	$83.30
Purchase #5	$50.61	6.290%	$53.7934	$53.79	$53.80	$53.80
Purchase #6	$78.52	4.252%	$81.8587	$81.86	$81.85	$81.90
Purchase #7	$55.85	11.508%	$62.2772	$62.28	$62.30	$62.30
7 purchase totals =	$839.89		$903.3411	$903.35	$903.40	$903.40