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	$80.75	5.701%	$85.3536	$85.35	$85.35	$85.40
Purchase #2	$130.89	7.124%	$140.2146	$140.21	$140.20	$140.20
Purchase #3	$42.59	6.372%	$45.3038	$45.30	$45.30	$45.30
Purchase #4	$33.76	7.223%	$36.1985	$36.20	$36.20	$36.20
Purchase #5	$9.88	6.389%	$10.5112	$10.51	$10.50	$10.50
Purchase #6	$95.54	5.654%	$100.9418	$100.94	$100.95	$100.90
Purchase #7	$216.83	13.517%	$246.1389	$246.14	$246.15	$246.10
7 purchase totals =	$610.24		$664.6624	$664.65	$664.65	$664.60