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	$36.46	11.764%	$40.7492	$40.75	$40.75	$40.70
Purchase #2	$148.64	6.329%	$158.0474	$158.05	$158.05	$158.00
Purchase #3	$5.51	13.393%	$6.248	$6.25	$6.25	$6.20
Purchase #4	$172.77	13.208%	$195.5895	$195.59	$195.60	$195.60
Purchase #5	$93.56	7.157%	$100.2561	$100.26	$100.25	$100.30
Purchase #6	$49.72	3.725%	$51.5721	$51.57	$51.55	$51.60
Purchase #7	$9.73	6.142%	$10.3276	$10.33	$10.35	$10.30
7 purchase totals =	$516.39		$562.7899	$562.80	$562.80	$562.70