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	$44.52	3.565%	$46.1071	$46.11	$46.10	$46.10
Purchase #2	$52.96	12.480%	$59.5694	$59.57	$59.55	$59.60
Purchase #3	$204.25	10.181%	$225.0447	$225.04	$225.05	$225.00
Purchase #4	$43.66	4.382%	$45.5732	$45.57	$45.55	$45.60
Purchase #5	$105.81	5.222%	$111.3354	$111.34	$111.35	$111.30
Purchase #6	$249.71	3.833%	$259.2814	$259.28	$259.30	$259.30
Purchase #7	$116.36	12.496%	$130.9003	$130.90	$130.90	$130.90
7 purchase totals =	$817.27		$877.8115	$877.81	$877.80	$877.80