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	$80.48	7.111%	$86.2029	$86.20	$86.20	$86.20
Purchase #2	$198.59	12.274%	$222.9649	$222.96	$222.95	$223.00
Purchase #3	$168.59	11.856%	$188.578	$188.58	$188.60	$188.60
Purchase #4	$46.94	12.412%	$52.7662	$52.77	$52.75	$52.80
Purchase #5	$250.34	13.575%	$284.3237	$284.32	$284.30	$284.30
Purchase #6	$205.29	13.853%	$233.7288	$233.73	$233.75	$233.70
Purchase #7	$178.88	9.395%	$195.6858	$195.69	$195.70	$195.70
7 purchase totals =	$1,129.11		$1,264.2503	$1,264.25	$1,264.25	$1,264.30