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	$168.66	13.208%	$190.9366	$190.94	$190.95	$190.90
Purchase #2	$63.56	11.560%	$70.9075	$70.91	$70.90	$70.90
Purchase #3	$214.73	3.741%	$222.763	$222.76	$222.75	$222.80
Purchase #4	$87.53	4.675%	$91.622	$91.62	$91.60	$91.60
Purchase #5	$165.29	13.784%	$188.0736	$188.07	$188.05	$188.10
Purchase #6	$20.61	3.851%	$21.4037	$21.40	$21.40	$21.40
Purchase #7	$174.90	12.131%	$196.1171	$196.12	$196.10	$196.10
7 purchase totals =	$895.28		$981.8235	$981.82	$981.75	$981.80