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	$31.65	13.437%	$35.9028	$35.90	$35.90	$35.90
Purchase #2	$19.38	7.545%	$20.8422	$20.84	$20.85	$20.80
Purchase #3	$30.79	5.480%	$32.4773	$32.48	$32.50	$32.50
Purchase #4	$218.43	8.667%	$237.3613	$237.36	$237.35	$237.40
Purchase #5	$22.75	6.311%	$24.1858	$24.19	$24.20	$24.20
Purchase #6	$64.88	11.192%	$72.1414	$72.14	$72.15	$72.10
Purchase #7	$116.69	5.734%	$123.381	$123.38	$123.40	$123.40
7 purchase totals =	$504.57		$546.2918	$546.29	$546.35	$546.30