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	$186.96	11.688%	$208.8119	$208.81	$208.80	$208.80
Purchase #2	$95.57	5.256%	$100.5932	$100.59	$100.60	$100.60
Purchase #3	$82.68	8.627%	$89.8128	$89.81	$89.80	$89.80
Purchase #4	$89.42	12.811%	$100.8756	$100.88	$100.90	$100.90
Purchase #5	$28.53	13.675%	$32.4315	$32.43	$32.45	$32.40
Purchase #6	$32.64	9.518%	$35.7467	$35.75	$35.75	$35.70
Purchase #7	$140.36	6.222%	$149.0932	$149.09	$149.10	$149.10
7 purchase totals =	$656.16		$717.3649	$717.36	$717.40	$717.30