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	$124.75	12.385%	$140.2003	$140.20	$140.20	$140.20
Purchase #2	$70.57	11.492%	$78.6799	$78.68	$78.70	$78.70
Purchase #3	$110.91	11.439%	$123.597	$123.60	$123.60	$123.60
Purchase #4	$136.32	6.257%	$144.8495	$144.85	$144.85	$144.80
Purchase #5	$185.84	12.790%	$209.6089	$209.61	$209.60	$209.60
Purchase #6	$29.93	10.690%	$33.1295	$33.13	$33.15	$33.10
Purchase #7	$159.44	3.804%	$165.5051	$165.51	$165.50	$165.50
7 purchase totals =	$817.76		$895.5702	$895.58	$895.60	$895.50