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	$96.47	13.607%	$109.5967	$109.60	$109.60	$109.60
Purchase #2	$177.50	10.338%	$195.85	$195.85	$195.85	$195.90
Purchase #3	$192.74	8.790%	$209.6818	$209.68	$209.70	$209.70
Purchase #4	$14.59	7.262%	$15.6495	$15.65	$15.65	$15.60
Purchase #5	$84.47	7.578%	$90.8711	$90.87	$90.85	$90.90
Purchase #6	$128.55	7.536%	$138.2375	$138.24	$138.25	$138.20
Purchase #7	$164.79	4.780%	$172.667	$172.67	$172.65	$172.70
7 purchase totals =	$859.11		$932.5536	$932.56	$932.55	$932.60