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	$7.57	5.118%	$7.9574	$7.96	$7.95	$8.00
Purchase #2	$68.48	8.705%	$74.4412	$74.44	$74.45	$74.40
Purchase #3	$194.71	5.234%	$204.9011	$204.90	$204.90	$204.90
Purchase #4	$42.89	6.375%	$45.6242	$45.62	$45.60	$45.60
Purchase #5	$49.38	10.395%	$54.5131	$54.51	$54.50	$54.50
Purchase #6	$19.72	8.659%	$21.4276	$21.43	$21.45	$21.40
Purchase #7	$219.52	8.240%	$237.6084	$237.61	$237.60	$237.60
7 purchase totals =	$602.27		$646.4730	$646.47	$646.45	$646.40