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	$127.60	3.731%	$132.3608	$132.36	$132.35	$132.40
Purchase #2	$119.51	11.355%	$133.0804	$133.08	$133.10	$133.10
Purchase #3	$63.61	13.683%	$72.3138	$72.31	$72.30	$72.30
Purchase #4	$169.55	3.363%	$175.252	$175.25	$175.25	$175.30
Purchase #5	$47.85	5.843%	$50.6459	$50.65	$50.65	$50.60
Purchase #6	$18.57	10.372%	$20.4961	$20.50	$20.50	$20.50
Purchase #7	$87.41	3.176%	$90.1861	$90.19	$90.20	$90.20
7 purchase totals =	$634.10		$674.3351	$674.34	$674.35	$674.40