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	$225.61	3.331%	$233.1251	$233.13	$233.15	$233.10
Purchase #2	$10.90	5.774%	$11.5294	$11.53	$11.55	$11.50
Purchase #3	$237.42	7.236%	$254.5997	$254.60	$254.60	$254.60
Purchase #4	$91.74	13.264%	$103.9084	$103.91	$103.90	$103.90
Purchase #5	$100.90	11.790%	$112.7961	$112.80	$112.80	$112.80
Purchase #6	$195.89	11.112%	$217.6573	$217.66	$217.65	$217.70
Purchase #7	$21.91	13.638%	$24.8981	$24.90	$24.90	$24.90
7 purchase totals =	$884.37		$958.5141	$958.53	$958.55	$958.50