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	$208.50	6.480%	$222.0108	$222.01	$222.00	$222.00
Purchase #2	$82.78	11.415%	$92.2293	$92.23	$92.25	$92.20
Purchase #3	$11.42	8.618%	$12.4042	$12.40	$12.40	$12.40
Purchase #4	$34.61	5.654%	$36.5668	$36.57	$36.55	$36.60
Purchase #5	$35.74	5.356%	$37.6542	$37.65	$37.65	$37.70
Purchase #6	$60.91	7.320%	$65.3686	$65.37	$65.35	$65.40
Purchase #7	$126.95	9.857%	$139.4635	$139.46	$139.45	$139.50
7 purchase totals =	$560.91		$605.6974	$605.69	$605.65	$605.80