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	$180.61	11.141%	$200.7318	$200.73	$200.75	$200.70
Purchase #2	$55.58	6.843%	$59.3833	$59.38	$59.40	$59.40
Purchase #3	$245.48	7.283%	$263.3583	$263.36	$263.35	$263.40
Purchase #4	$26.96	6.518%	$28.7173	$28.72	$28.70	$28.70
Purchase #5	$129.60	10.244%	$142.8762	$142.88	$142.90	$142.90
Purchase #6	$125.25	9.422%	$137.0511	$137.05	$137.05	$137.10
Purchase #7	$11.90	7.817%	$12.8302	$12.83	$12.85	$12.80
7 purchase totals =	$775.38		$844.9482	$844.95	$845.00	$845.00