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	$48.38	6.309%	$51.4323	$51.43	$51.45	$51.40
Purchase #2	$39.49	8.797%	$42.9639	$42.96	$42.95	$43.00
Purchase #3	$38.72	5.372%	$40.8	$40.80	$40.80	$40.80
Purchase #4	$141.48	11.755%	$158.111	$158.11	$158.10	$158.10
Purchase #5	$12.60	8.346%	$13.6516	$13.65	$13.65	$13.70
Purchase #6	$42.75	4.383%	$44.6237	$44.62	$44.60	$44.60
Purchase #7	$68.45	12.343%	$76.8988	$76.90	$76.90	$76.90
7 purchase totals =	$391.87		$428.4813	$428.47	$428.45	$428.50