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	$130.97	13.284%	$148.3681	$148.37	$148.35	$148.40
Purchase #2	$12.35	4.240%	$12.8736	$12.87	$12.85	$12.90
Purchase #3	$47.47	11.556%	$52.9556	$52.96	$52.95	$53.00
Purchase #4	$10.53	12.447%	$11.8407	$11.84	$11.85	$11.80
Purchase #5	$42.38	5.501%	$44.7113	$44.71	$44.70	$44.70
Purchase #6	$83.98	8.123%	$90.8017	$90.80	$90.80	$90.80
Purchase #7	$194.60	3.244%	$200.9128	$200.91	$200.90	$200.90
7 purchase totals =	$522.28		$562.4638	$562.46	$562.40	$562.50