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	$214.34	13.123%	$242.4678	$242.47	$242.45	$242.50
Purchase #2	$197.35	10.675%	$218.4171	$218.42	$218.40	$218.40
Purchase #3	$190.69	11.568%	$212.749	$212.75	$212.75	$212.70
Purchase #4	$36.85	10.514%	$40.7244	$40.72	$40.70	$40.70
Purchase #5	$70.46	11.317%	$78.434	$78.43	$78.45	$78.40
Purchase #6	$169.68	7.336%	$182.1277	$182.13	$182.15	$182.10
Purchase #7	$89.96	4.313%	$93.84	$93.84	$93.85	$93.80
7 purchase totals =	$969.33		$1,068.7600	$1,068.76	$1,068.75	$1,068.60