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	$148.84	12.643%	$167.6578	$167.66	$167.65	$167.70
Purchase #2	$171.42	12.223%	$192.3727	$192.37	$192.35	$192.40
Purchase #3	$116.38	7.776%	$125.4297	$125.43	$125.45	$125.40
Purchase #4	$18.82	4.224%	$19.615	$19.62	$19.60	$19.60
Purchase #5	$86.35	10.388%	$95.32	$95.32	$95.30	$95.30
Purchase #6	$50.29	12.373%	$56.5124	$56.51	$56.50	$56.50
Purchase #7	$6.36	10.815%	$7.0478	$7.05	$7.05	$7.00
7 purchase totals =	$598.46		$663.9554	$663.96	$663.90	$663.90