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	$38.43	11.195%	$42.7322	$42.73	$42.75	$42.70
Purchase #2	$10.27	9.108%	$11.2054	$11.21	$11.20	$11.20
Purchase #3	$244.83	10.840%	$271.3696	$271.37	$271.35	$271.40
Purchase #4	$145.90	3.675%	$151.2618	$151.26	$151.25	$151.30
Purchase #5	$29.94	11.744%	$33.4562	$33.46	$33.45	$33.50
Purchase #6	$192.82	3.584%	$199.7307	$199.73	$199.75	$199.70
Purchase #7	$32.25	11.858%	$36.0742	$36.07	$36.05	$36.10
7 purchase totals =	$694.44		$745.8301	$745.83	$745.80	$745.90