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	$52.81	11.817%	$59.0506	$59.05	$59.05	$59.10
Purchase #2	$13.50	12.225%	$15.1504	$15.15	$15.15	$15.20
Purchase #3	$85.41	5.193%	$89.8453	$89.85	$89.85	$89.80
Purchase #4	$32.70	13.573%	$37.1384	$37.14	$37.15	$37.10
Purchase #5	$76.40	11.138%	$84.9094	$84.91	$84.90	$84.90
Purchase #6	$169.31	11.725%	$189.1616	$189.16	$189.15	$189.20
Purchase #7	$164.84	13.274%	$186.7209	$186.72	$186.70	$186.70
7 purchase totals =	$594.97		$661.9766	$661.98	$661.95	$662.00