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	$57.79	3.573%	$59.8548	$59.85	$59.85	$59.90
Purchase #2	$64.90	10.720%	$71.8573	$71.86	$71.85	$71.90
Purchase #3	$155.80	3.738%	$161.6238	$161.62	$161.60	$161.60
Purchase #4	$22.41	11.300%	$24.9423	$24.94	$24.95	$24.90
Purchase #5	$84.71	3.236%	$87.4512	$87.45	$87.45	$87.50
Purchase #6	$90.49	11.305%	$100.7199	$100.72	$100.70	$100.70
Purchase #7	$31.25	5.103%	$32.8447	$32.84	$32.85	$32.80
7 purchase totals =	$507.35		$539.2940	$539.28	$539.25	$539.30