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	$158.99	12.692%	$179.169	$179.17	$179.15	$179.20
Purchase #2	$140.82	5.725%	$148.8819	$148.88	$148.90	$148.90
Purchase #3	$214.29	9.595%	$234.8511	$234.85	$234.85	$234.90
Purchase #4	$185.54	5.845%	$196.3848	$196.38	$196.40	$196.40
Purchase #5	$69.54	9.256%	$75.9766	$75.98	$76.00	$76.00
Purchase #6	$194.26	11.219%	$216.054	$216.05	$216.05	$216.10
Purchase #7	$151.90	13.749%	$172.7847	$172.78	$172.80	$172.80
7 purchase totals =	$1,115.34		$1,224.1021	$1,224.09	$1,224.15	$1,224.30