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	$183.51	8.508%	$199.123	$199.12	$199.10	$199.10
Purchase #2	$246.61	11.749%	$275.5842	$275.58	$275.60	$275.60
Purchase #3	$10.56	12.853%	$11.9173	$11.92	$11.90	$11.90
Purchase #4	$147.48	9.340%	$161.2546	$161.25	$161.25	$161.30
Purchase #5	$89.64	4.615%	$93.7769	$93.78	$93.80	$93.80
Purchase #6	$37.89	11.151%	$42.1151	$42.12	$42.10	$42.10
Purchase #7	$200.79	13.315%	$227.5252	$227.53	$227.55	$227.50
7 purchase totals =	$916.48		$1,011.2963	$1,011.30	$1,011.30	$1,011.30