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	$83.88	8.133%	$90.702	$90.70	$90.70	$90.70
Purchase #2	$82.29	12.434%	$92.5219	$92.52	$92.50	$92.50
Purchase #3	$87.63	12.403%	$98.4987	$98.50	$98.50	$98.50
Purchase #4	$45.85	9.405%	$50.1622	$50.16	$50.15	$50.20
Purchase #5	$114.86	4.106%	$119.5762	$119.58	$119.60	$119.60
Purchase #6	$193.70	3.638%	$200.7468	$200.75	$200.75	$200.70
Purchase #7	$238.42	10.851%	$264.291	$264.29	$264.30	$264.30
7 purchase totals =	$846.63		$916.4988	$916.50	$916.50	$916.50