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	$196.65	13.589%	$223.3728	$223.37	$223.35	$223.40
Purchase #2	$182.96	4.151%	$190.5547	$190.55	$190.55	$190.60
Purchase #3	$165.57	12.302%	$185.9384	$185.94	$185.95	$185.90
Purchase #4	$26.50	13.382%	$30.0462	$30.05	$30.05	$30.00
Purchase #5	$52.94	13.208%	$59.9323	$59.93	$59.95	$59.90
Purchase #6	$18.41	13.749%	$20.9412	$20.94	$20.95	$20.90
Purchase #7	$92.51	13.368%	$104.8767	$104.88	$104.90	$104.90
7 purchase totals =	$735.54		$815.6623	$815.66	$815.70	$815.60