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	$247.63	6.434%	$263.5625	$263.56	$263.55	$263.60
Purchase #2	$35.32	13.684%	$40.1532	$40.15	$40.15	$40.20
Purchase #3	$174.68	8.787%	$190.0291	$190.03	$190.05	$190.00
Purchase #4	$88.67	7.857%	$95.6368	$95.64	$95.65	$95.60
Purchase #5	$179.35	7.201%	$192.265	$192.27	$192.25	$192.30
Purchase #6	$162.59	4.105%	$169.2643	$169.26	$169.25	$169.30
Purchase #7	$40.73	12.796%	$45.9418	$45.94	$45.95	$45.90
7 purchase totals =	$928.97		$996.8527	$996.85	$996.85	$996.90