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	$102.41	3.444%	$105.937	$105.94	$105.95	$105.90
Purchase #2	$175.78	8.338%	$190.4365	$190.44	$190.45	$190.40
Purchase #3	$202.72	11.456%	$225.9436	$225.94	$225.95	$225.90
Purchase #4	$37.53	5.301%	$39.5195	$39.52	$39.50	$39.50
Purchase #5	$39.89	11.303%	$44.3988	$44.40	$44.40	$44.40
Purchase #6	$198.84	4.682%	$208.1497	$208.15	$208.15	$208.10
Purchase #7	$209.33	7.111%	$224.2155	$224.22	$224.20	$224.20
7 purchase totals =	$966.50		$1,038.6006	$1,038.61	$1,038.60	$1,038.40