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	$230.34	12.417%	$258.9413	$258.94	$258.95	$258.90
Purchase #2	$7.81	10.124%	$8.6007	$8.60	$8.60	$8.60
Purchase #3	$40.55	10.722%	$44.8978	$44.90	$44.90	$44.90
Purchase #4	$46.77	8.828%	$50.8989	$50.90	$50.90	$50.90
Purchase #5	$17.93	13.710%	$20.3882	$20.39	$20.40	$20.40
Purchase #6	$222.90	12.781%	$251.3888	$251.39	$251.40	$251.40
Purchase #7	$18.41	13.511%	$20.8974	$20.90	$20.90	$20.90
7 purchase totals =	$584.71		$656.0131	$656.02	$656.05	$656.00