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	$215.97	11.171%	$240.096	$240.10	$240.10	$240.10
Purchase #2	$33.47	10.742%	$37.0653	$37.07	$37.05	$37.10
Purchase #3	$125.50	3.587%	$130.0017	$130.00	$130.00	$130.00
Purchase #4	$32.67	5.490%	$34.4636	$34.46	$34.45	$34.50
Purchase #5	$75.73	9.194%	$82.6926	$82.69	$82.70	$82.70
Purchase #6	$228.63	12.304%	$256.7606	$256.76	$256.75	$256.80
Purchase #7	$226.64	10.219%	$249.8003	$249.80	$249.80	$249.80
7 purchase totals =	$938.61		$1,030.8801	$1,030.88	$1,030.85	$1,031.00