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	$106.93	11.719%	$119.4611	$119.46	$119.45	$119.50
Purchase #2	$35.65	13.244%	$40.3715	$40.37	$40.35	$40.40
Purchase #3	$155.37	13.530%	$176.3916	$176.39	$176.40	$176.40
Purchase #4	$18.81	8.431%	$20.3959	$20.40	$20.40	$20.40
Purchase #5	$69.81	13.379%	$79.1499	$79.15	$79.15	$79.10
Purchase #6	$78.53	4.765%	$82.272	$82.27	$82.25	$82.30
Purchase #7	$6.52	7.826%	$7.0303	$7.03	$7.05	$7.00
7 purchase totals =	$471.62		$525.0723	$525.07	$525.05	$525.10