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	$137.63	3.390%	$142.2957	$142.30	$142.30	$142.30
Purchase #2	$66.54	13.694%	$75.652	$75.65	$75.65	$75.70
Purchase #3	$32.63	7.520%	$35.0838	$35.08	$35.10	$35.10
Purchase #4	$63.54	12.167%	$71.2709	$71.27	$71.25	$71.30
Purchase #5	$174.81	6.686%	$186.4978	$186.50	$186.50	$186.50
Purchase #6	$92.87	7.800%	$100.1139	$100.11	$100.10	$100.10
Purchase #7	$164.45	6.678%	$175.432	$175.43	$175.45	$175.40
7 purchase totals =	$732.47		$786.3461	$786.34	$786.35	$786.40