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	$32.86	13.657%	$37.3477	$37.35	$37.35	$37.30
Purchase #2	$167.72	13.637%	$190.592	$190.59	$190.60	$190.60
Purchase #3	$13.52	7.319%	$14.5095	$14.51	$14.50	$14.50
Purchase #4	$78.48	6.266%	$83.3976	$83.40	$83.40	$83.40
Purchase #5	$149.43	12.519%	$168.1371	$168.14	$168.15	$168.10
Purchase #6	$98.35	8.684%	$106.8907	$106.89	$106.90	$106.90
Purchase #7	$182.99	9.693%	$200.7272	$200.73	$200.75	$200.70
7 purchase totals =	$723.35		$801.6018	$801.61	$801.65	$801.50