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	$203.93	4.156%	$212.4053	$212.41	$212.40	$212.40
Purchase #2	$37.68	7.696%	$40.5799	$40.58	$40.60	$40.60
Purchase #3	$87.72	7.425%	$94.2332	$94.23	$94.25	$94.20
Purchase #4	$168.42	3.131%	$173.6932	$173.69	$173.70	$173.70
Purchase #5	$65.56	3.234%	$67.6802	$67.68	$67.70	$67.70
Purchase #6	$247.40	3.312%	$255.5939	$255.59	$255.60	$255.60
Purchase #7	$59.66	9.243%	$65.1744	$65.17	$65.15	$65.20
7 purchase totals =	$870.37		$909.3601	$909.35	$909.40	$909.40