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	$221.28	9.287%	$241.8303	$241.83	$241.85	$241.80
Purchase #2	$200.83	11.277%	$223.4776	$223.48	$223.50	$223.50
Purchase #3	$238.66	5.513%	$251.8173	$251.82	$251.80	$251.80
Purchase #4	$189.84	5.762%	$200.7786	$200.78	$200.80	$200.80
Purchase #5	$176.87	4.660%	$185.1121	$185.11	$185.10	$185.10
Purchase #6	$116.80	3.367%	$120.7327	$120.73	$120.75	$120.70
Purchase #7	$162.61	8.241%	$176.0107	$176.01	$176.00	$176.00
7 purchase totals =	$1,306.89		$1,399.7593	$1,399.76	$1,399.80	$1,399.70