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	$196.84	4.494%	$205.686	$205.69	$205.70	$205.70
Purchase #2	$103.33	8.191%	$111.7938	$111.79	$111.80	$111.80
Purchase #3	$87.71	7.726%	$94.4865	$94.49	$94.50	$94.50
Purchase #4	$133.92	5.178%	$140.8544	$140.85	$140.85	$140.90
Purchase #5	$148.63	11.306%	$165.4341	$165.43	$165.45	$165.40
Purchase #6	$185.58	3.313%	$191.7283	$191.73	$191.75	$191.70
Purchase #7	$10.39	9.412%	$11.3679	$11.37	$11.35	$11.40
7 purchase totals =	$866.40		$921.3510	$921.35	$921.40	$921.40