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	$68.50	3.280%	$70.7468	$70.75	$70.75	$70.70
Purchase #2	$10.57	3.514%	$10.9414	$10.94	$10.95	$10.90
Purchase #3	$47.65	6.233%	$50.62	$50.62	$50.60	$50.60
Purchase #4	$60.29	4.307%	$62.8867	$62.89	$62.90	$62.90
Purchase #5	$34.77	6.141%	$36.9052	$36.91	$36.90	$36.90
Purchase #6	$80.87	11.508%	$90.1765	$90.18	$90.20	$90.20
Purchase #7	$167.66	13.844%	$190.8709	$190.87	$190.85	$190.90
7 purchase totals =	$470.31		$513.1475	$513.16	$513.15	$513.10