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	$184.26	13.468%	$209.0761	$209.08	$209.10	$209.10
Purchase #2	$50.78	4.682%	$53.1575	$53.16	$53.15	$53.20
Purchase #3	$200.34	12.759%	$225.9014	$225.90	$225.90	$225.90
Purchase #4	$114.47	4.863%	$120.0367	$120.04	$120.05	$120.00
Purchase #5	$151.46	11.244%	$168.4902	$168.49	$168.50	$168.50
Purchase #6	$6.54	4.460%	$6.8317	$6.83	$6.85	$6.80
Purchase #7	$106.91	12.821%	$120.6169	$120.62	$120.60	$120.60
7 purchase totals =	$814.76		$904.1105	$904.12	$904.15	$904.10