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	$152.31	3.511%	$157.6576	$157.66	$157.65	$157.70
Purchase #2	$217.35	12.689%	$244.9295	$244.93	$244.95	$244.90
Purchase #3	$100.71	13.841%	$114.6493	$114.65	$114.65	$114.60
Purchase #4	$123.45	13.237%	$139.7911	$139.79	$139.80	$139.80
Purchase #5	$34.37	13.698%	$39.078	$39.08	$39.10	$39.10
Purchase #6	$91.70	7.417%	$98.5014	$98.50	$98.50	$98.50
Purchase #7	$53.60	11.660%	$59.8498	$59.85	$59.85	$59.80
7 purchase totals =	$773.49		$854.4567	$854.46	$854.50	$854.40