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	$182.55	6.547%	$194.5015	$194.50	$194.50	$194.50
Purchase #2	$221.55	7.504%	$238.1751	$238.18	$238.20	$238.20
Purchase #3	$34.67	8.216%	$37.5185	$37.52	$37.50	$37.50
Purchase #4	$45.45	10.620%	$50.2768	$50.28	$50.30	$50.30
Purchase #5	$165.84	9.490%	$181.5782	$181.58	$181.60	$181.60
Purchase #6	$161.90	12.345%	$181.8866	$181.89	$181.90	$181.90
Purchase #7	$230.86	9.110%	$251.8913	$251.89	$251.90	$251.90
7 purchase totals =	$1,042.82		$1,135.8280	$1,135.84	$1,135.90	$1,135.90