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	$76.64	7.705%	$82.5451	$82.55	$82.55	$82.50
Purchase #2	$78.75	3.292%	$81.3425	$81.34	$81.35	$81.30
Purchase #3	$37.80	8.798%	$41.1256	$41.13	$41.15	$41.10
Purchase #4	$12.78	6.507%	$13.6116	$13.61	$13.60	$13.60
Purchase #5	$37.75	13.489%	$42.8421	$42.84	$42.85	$42.80
Purchase #6	$114.28	10.767%	$126.5845	$126.58	$126.60	$126.60
Purchase #7	$223.84	7.408%	$240.4221	$240.42	$240.40	$240.40
7 purchase totals =	$581.84		$628.4735	$628.47	$628.50	$628.30