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	$165.41	10.288%	$182.4274	$182.43	$182.45	$182.40
Purchase #2	$220.63	8.244%	$238.8187	$238.82	$238.80	$238.80
Purchase #3	$148.78	6.371%	$158.2588	$158.26	$158.25	$158.30
Purchase #4	$9.87	3.874%	$10.2524	$10.25	$10.25	$10.30
Purchase #5	$37.86	12.822%	$42.7144	$42.71	$42.70	$42.70
Purchase #6	$122.59	6.547%	$130.616	$130.62	$130.60	$130.60
Purchase #7	$198.35	11.643%	$221.4439	$221.44	$221.45	$221.40
7 purchase totals =	$903.49		$984.5316	$984.53	$984.50	$984.50