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	$182.83	9.299%	$199.8314	$199.83	$199.85	$199.80
Purchase #2	$147.77	5.657%	$156.1293	$156.13	$156.15	$156.10
Purchase #3	$50.68	10.639%	$56.0718	$56.07	$56.05	$56.10
Purchase #4	$165.59	4.392%	$172.8627	$172.86	$172.85	$172.90
Purchase #5	$79.65	13.723%	$90.5804	$90.58	$90.60	$90.60
Purchase #6	$34.26	5.480%	$36.1374	$36.14	$36.15	$36.10
Purchase #7	$214.78	7.350%	$230.5663	$230.57	$230.55	$230.60
7 purchase totals =	$875.56		$942.1793	$942.18	$942.20	$942.20