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	$53.46	10.773%	$59.2192	$59.22	$59.20	$59.20
Purchase #2	$241.37	9.273%	$263.7522	$263.75	$263.75	$263.80
Purchase #3	$157.86	7.854%	$170.2583	$170.26	$170.25	$170.30
Purchase #4	$129.53	12.782%	$146.0865	$146.09	$146.10	$146.10
Purchase #5	$134.89	4.489%	$140.9452	$140.95	$140.95	$140.90
Purchase #6	$199.86	12.651%	$225.1443	$225.14	$225.15	$225.10
Purchase #7	$35.74	13.260%	$40.4791	$40.48	$40.50	$40.50
7 purchase totals =	$952.71		$1,045.8848	$1,045.89	$1,045.90	$1,045.90