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	$85.74	13.580%	$97.3835	$97.38	$97.40	$97.40
Purchase #2	$230.73	11.209%	$256.5925	$256.59	$256.60	$256.60
Purchase #3	$22.50	5.584%	$23.7564	$23.76	$23.75	$23.80
Purchase #4	$83.81	11.768%	$93.6728	$93.67	$93.65	$93.70
Purchase #5	$145.35	8.707%	$158.0056	$158.01	$158.00	$158.00
Purchase #6	$174.64	6.246%	$185.548	$185.55	$185.55	$185.50
Purchase #7	$178.72	10.175%	$196.9048	$196.90	$196.90	$196.90
7 purchase totals =	$921.49		$1,011.8636	$1,011.86	$1,011.85	$1,011.90