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	$42.62	4.249%	$44.4309	$44.43	$44.45	$44.40
Purchase #2	$128.30	7.414%	$137.8122	$137.81	$137.80	$137.80
Purchase #3	$45.28	11.705%	$50.58	$50.58	$50.60	$50.60
Purchase #4	$57.48	3.338%	$59.3987	$59.40	$59.40	$59.40
Purchase #5	$88.31	11.724%	$98.6635	$98.66	$98.65	$98.70
Purchase #6	$189.86	12.500%	$213.5925	$213.59	$213.60	$213.60
Purchase #7	$147.47	8.320%	$159.7395	$159.74	$159.75	$159.70
7 purchase totals =	$699.32		$764.2173	$764.21	$764.25	$764.20