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	$172.89	13.718%	$196.6071	$196.61	$196.60	$196.60
Purchase #2	$9.75	11.732%	$10.8939	$10.89	$10.90	$10.90
Purchase #3	$205.36	3.676%	$212.909	$212.91	$212.90	$212.90
Purchase #4	$145.32	13.530%	$164.9818	$164.98	$165.00	$165.00
Purchase #5	$137.35	13.526%	$155.928	$155.93	$155.95	$155.90
Purchase #6	$206.40	13.420%	$234.0989	$234.10	$234.10	$234.10
Purchase #7	$20.47	7.704%	$22.047	$22.05	$22.05	$22.00
7 purchase totals =	$897.54		$997.4657	$997.47	$997.50	$997.40