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	$223.57	12.601%	$251.7421	$251.74	$251.75	$251.70
Purchase #2	$211.90	5.477%	$223.5058	$223.51	$223.50	$223.50
Purchase #3	$183.84	4.767%	$192.6037	$192.60	$192.60	$192.60
Purchase #4	$171.78	5.336%	$180.9462	$180.95	$180.95	$180.90
Purchase #5	$247.78	3.117%	$255.5033	$255.50	$255.50	$255.50
Purchase #6	$141.78	6.164%	$150.5193	$150.52	$150.50	$150.50
Purchase #7	$126.32	12.611%	$142.2502	$142.25	$142.25	$142.30
7 purchase totals =	$1,306.97		$1,397.0706	$1,397.07	$1,397.05	$1,397.00