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	$125.41	13.142%	$141.8914	$141.89	$141.90	$141.90
Purchase #2	$75.51	12.497%	$84.9465	$84.95	$84.95	$84.90
Purchase #3	$73.51	5.367%	$77.4553	$77.46	$77.45	$77.50
Purchase #4	$110.51	6.103%	$117.2544	$117.25	$117.25	$117.30
Purchase #5	$81.41	6.162%	$86.4265	$86.43	$86.45	$86.40
Purchase #6	$244.47	4.121%	$254.5446	$254.54	$254.55	$254.50
Purchase #7	$242.59	12.490%	$272.8895	$272.89	$272.90	$272.90
7 purchase totals =	$953.41		$1,035.4082	$1,035.41	$1,035.45	$1,035.40