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	$151.83	12.688%	$171.0942	$171.09	$171.10	$171.10
Purchase #2	$84.28	13.293%	$95.4833	$95.48	$95.50	$95.50
Purchase #3	$62.86	13.251%	$71.1896	$71.19	$71.20	$71.20
Purchase #4	$101.60	11.559%	$113.3439	$113.34	$113.35	$113.30
Purchase #5	$57.28	7.525%	$61.5903	$61.59	$61.60	$61.60
Purchase #6	$229.57	4.230%	$239.2808	$239.28	$239.30	$239.30
Purchase #7	$126.42	13.172%	$143.072	$143.07	$143.05	$143.10
7 purchase totals =	$813.84		$895.0541	$895.04	$895.10	$895.10