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	$151.98	8.368%	$164.6977	$164.70	$164.70	$164.70
Purchase #2	$179.90	7.218%	$192.8852	$192.89	$192.90	$192.90
Purchase #3	$31.59	3.204%	$32.6021	$32.60	$32.60	$32.60
Purchase #4	$32.74	5.468%	$34.5302	$34.53	$34.55	$34.50
Purchase #5	$30.54	4.602%	$31.9455	$31.95	$31.95	$31.90
Purchase #6	$60.45	6.587%	$64.4318	$64.43	$64.45	$64.40
Purchase #7	$79.94	13.581%	$90.7967	$90.80	$90.80	$90.80
7 purchase totals =	$567.14		$611.8892	$611.90	$611.95	$611.80