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	$125.70	5.307%	$132.3709	$132.37	$132.35	$132.40
Purchase #2	$64.85	10.813%	$71.8622	$71.86	$71.85	$71.90
Purchase #3	$63.65	6.634%	$67.8725	$67.87	$67.85	$67.90
Purchase #4	$140.34	11.733%	$156.8061	$156.81	$156.80	$156.80
Purchase #5	$208.32	6.316%	$221.4775	$221.48	$221.50	$221.50
Purchase #6	$234.77	9.603%	$257.315	$257.32	$257.30	$257.30
Purchase #7	$52.43	6.308%	$55.7373	$55.74	$55.75	$55.70
7 purchase totals =	$890.06		$963.4415	$963.45	$963.40	$963.50