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	$53.41	11.425%	$59.5121	$59.51	$59.50	$59.50
Purchase #2	$81.92	11.537%	$91.3711	$91.37	$91.35	$91.40
Purchase #3	$119.59	5.529%	$126.2021	$126.20	$126.20	$126.20
Purchase #4	$76.96	10.155%	$84.7753	$84.78	$84.80	$84.80
Purchase #5	$49.25	11.301%	$54.8157	$54.82	$54.80	$54.80
Purchase #6	$53.82	13.872%	$61.2859	$61.29	$61.30	$61.30
Purchase #7	$11.54	8.836%	$12.5597	$12.56	$12.55	$12.60
7 purchase totals =	$446.49		$490.5219	$490.53	$490.50	$490.60