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	$91.73	4.127%	$95.5157	$95.52	$95.50	$95.50
Purchase #2	$142.29	11.445%	$158.5751	$158.58	$158.60	$158.60
Purchase #3	$199.49	11.273%	$221.9785	$221.98	$222.00	$222.00
Purchase #4	$232.47	13.723%	$264.3719	$264.37	$264.35	$264.40
Purchase #5	$230.38	12.639%	$259.4977	$259.50	$259.50	$259.50
Purchase #6	$211.42	8.600%	$229.6021	$229.60	$229.60	$229.60
Purchase #7	$193.74	3.443%	$200.4105	$200.41	$200.40	$200.40
7 purchase totals =	$1,301.52		$1,429.9515	$1,429.96	$1,429.95	$1,430.00