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	$57.35	7.663%	$61.7447	$61.74	$61.75	$61.70
Purchase #2	$35.51	13.139%	$40.1757	$40.18	$40.20	$40.20
Purchase #3	$40.57	3.706%	$42.0735	$42.07	$42.05	$42.10
Purchase #4	$242.37	5.408%	$255.4774	$255.48	$255.50	$255.50
Purchase #5	$180.25	6.247%	$191.5102	$191.51	$191.50	$191.50
Purchase #6	$182.28	5.756%	$192.772	$192.77	$192.75	$192.80
Purchase #7	$208.93	9.578%	$228.9413	$228.94	$228.95	$228.90
7 purchase totals =	$947.26		$1,012.6948	$1,012.69	$1,012.70	$1,012.70