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	$89.83	6.702%	$95.8504	$95.85	$95.85	$95.90
Purchase #2	$101.61	8.855%	$110.6076	$110.61	$110.60	$110.60
Purchase #3	$139.71	5.402%	$147.2571	$147.26	$147.25	$147.30
Purchase #4	$75.37	4.788%	$78.9787	$78.98	$79.00	$79.00
Purchase #5	$18.74	9.201%	$20.4643	$20.46	$20.45	$20.50
Purchase #6	$35.79	5.571%	$37.7839	$37.78	$37.80	$37.80
Purchase #7	$203.43	13.364%	$230.6164	$230.62	$230.60	$230.60
7 purchase totals =	$664.48		$721.5584	$721.56	$721.55	$721.70