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	$116.27	6.659%	$124.0124	$124.01	$124.00	$124.00
Purchase #2	$244.61	11.635%	$273.0704	$273.07	$273.05	$273.10
Purchase #3	$35.54	7.568%	$38.2297	$38.23	$38.25	$38.20
Purchase #4	$187.37	11.265%	$208.4772	$208.48	$208.50	$208.50
Purchase #5	$28.40	5.286%	$29.9012	$29.90	$29.90	$29.90
Purchase #6	$222.87	6.828%	$238.0876	$238.09	$238.10	$238.10
Purchase #7	$94.77	5.550%	$100.0297	$100.03	$100.05	$100.00
7 purchase totals =	$929.83		$1,011.8082	$1,011.81	$1,011.85	$1,011.80