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	$20.77	5.183%	$21.8465	$21.85	$21.85	$21.80
Purchase #2	$6.86	8.181%	$7.4212	$7.42	$7.40	$7.40
Purchase #3	$209.59	6.709%	$223.6514	$223.65	$223.65	$223.70
Purchase #4	$29.79	5.462%	$31.4171	$31.42	$31.40	$31.40
Purchase #5	$116.90	6.134%	$124.0706	$124.07	$124.05	$124.10
Purchase #6	$91.37	10.110%	$100.6075	$100.61	$100.60	$100.60
Purchase #7	$178.60	9.575%	$195.701	$195.70	$195.70	$195.70
7 purchase totals =	$653.88		$704.7153	$704.72	$704.65	$704.70