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	$83.47	11.102%	$92.7368	$92.74	$92.75	$92.70
Purchase #2	$246.95	10.763%	$273.5292	$273.53	$273.55	$273.50
Purchase #3	$158.82	6.149%	$168.5858	$168.59	$168.60	$168.60
Purchase #4	$27.63	7.555%	$29.7174	$29.72	$29.70	$29.70
Purchase #5	$30.96	10.306%	$34.1507	$34.15	$34.15	$34.20
Purchase #6	$79.60	13.820%	$90.6007	$90.60	$90.60	$90.60
Purchase #7	$244.35	11.522%	$272.504	$272.50	$272.50	$272.50
7 purchase totals =	$871.78		$961.8246	$961.83	$961.85	$961.80