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	$87.26	6.229%	$92.6954	$92.70	$92.70	$92.70
Purchase #2	$103.37	12.840%	$116.6427	$116.64	$116.65	$116.60
Purchase #3	$12.88	11.821%	$14.4025	$14.40	$14.40	$14.40
Purchase #4	$6.89	12.271%	$7.7355	$7.74	$7.75	$7.70
Purchase #5	$32.96	3.763%	$34.2003	$34.20	$34.20	$34.20
Purchase #6	$52.48	6.597%	$55.9421	$55.94	$55.95	$55.90
Purchase #7	$55.75	6.249%	$59.2338	$59.23	$59.25	$59.20
7 purchase totals =	$351.59		$380.8523	$380.85	$380.90	$380.70