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	$180.71	11.160%	$200.8772	$200.88	$200.90	$200.90
Purchase #2	$84.31	12.802%	$95.1034	$95.10	$95.10	$95.10
Purchase #3	$199.67	4.218%	$208.0921	$208.09	$208.10	$208.10
Purchase #4	$238.46	7.385%	$256.0703	$256.07	$256.05	$256.10
Purchase #5	$32.45	7.188%	$34.7825	$34.78	$34.80	$34.80
Purchase #6	$190.27	13.448%	$215.8575	$215.86	$215.85	$215.90
Purchase #7	$8.32	6.467%	$8.8581	$8.86	$8.85	$8.90
7 purchase totals =	$934.19		$1,019.6411	$1,019.64	$1,019.65	$1,019.80