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	$100.94	10.332%	$111.3691	$111.37	$111.35	$111.40
Purchase #2	$84.90	7.161%	$90.9797	$90.98	$91.00	$91.00
Purchase #3	$37.72	3.376%	$38.9934	$38.99	$39.00	$39.00
Purchase #4	$177.38	13.301%	$200.9733	$200.97	$200.95	$201.00
Purchase #5	$192.82	12.289%	$216.5156	$216.52	$216.50	$216.50
Purchase #6	$183.89	12.473%	$206.8266	$206.83	$206.85	$206.80
Purchase #7	$221.39	7.844%	$238.7558	$238.76	$238.75	$238.80
7 purchase totals =	$999.04		$1,104.4135	$1,104.42	$1,104.40	$1,104.50