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	$124.46	12.853%	$140.4568	$140.46	$140.45	$140.50
Purchase #2	$34.72	6.810%	$37.0844	$37.08	$37.10	$37.10
Purchase #3	$172.80	9.611%	$189.4078	$189.41	$189.40	$189.40
Purchase #4	$238.31	10.637%	$263.659	$263.66	$263.65	$263.70
Purchase #5	$155.58	6.662%	$165.9447	$165.94	$165.95	$165.90
Purchase #6	$157.44	11.537%	$175.6039	$175.60	$175.60	$175.60
Purchase #7	$213.53	11.792%	$238.7095	$238.71	$238.70	$238.70
7 purchase totals =	$1,096.84		$1,210.8661	$1,210.86	$1,210.85	$1,210.90