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	$144.91	7.383%	$155.6087	$155.61	$155.60	$155.60
Purchase #2	$198.61	13.582%	$225.5852	$225.59	$225.60	$225.60
Purchase #3	$67.39	4.785%	$70.6146	$70.61	$70.60	$70.60
Purchase #4	$28.64	10.207%	$31.5633	$31.56	$31.55	$31.60
Purchase #5	$103.63	10.458%	$114.4676	$114.47	$114.45	$114.50
Purchase #6	$125.78	11.745%	$140.5529	$140.55	$140.55	$140.60
Purchase #7	$177.51	8.255%	$192.1635	$192.16	$192.15	$192.20
7 purchase totals =	$846.47		$930.5558	$930.55	$930.50	$930.70