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	$190.67	5.313%	$200.8003	$200.80	$200.80	$200.80
Purchase #2	$169.73	11.557%	$189.3457	$189.35	$189.35	$189.30
Purchase #3	$152.58	3.799%	$158.3765	$158.38	$158.40	$158.40
Purchase #4	$88.78	12.257%	$99.6618	$99.66	$99.65	$99.70
Purchase #5	$104.26	6.620%	$111.162	$111.16	$111.15	$111.20
Purchase #6	$195.47	7.237%	$209.6162	$209.62	$209.60	$209.60
Purchase #7	$22.34	10.593%	$24.7065	$24.71	$24.70	$24.70
7 purchase totals =	$923.83		$993.6690	$993.68	$993.65	$993.70