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	$210.48	9.452%	$230.3746	$230.37	$230.35	$230.40
Purchase #2	$228.52	9.597%	$250.4511	$250.45	$250.45	$250.50
Purchase #3	$116.45	13.212%	$131.8354	$131.84	$131.85	$131.80
Purchase #4	$106.95	6.674%	$114.0878	$114.09	$114.10	$114.10
Purchase #5	$202.68	6.841%	$216.5453	$216.55	$216.55	$216.50
Purchase #6	$82.73	11.105%	$91.9172	$91.92	$91.90	$91.90
Purchase #7	$6.80	10.412%	$7.508	$7.51	$7.50	$7.50
7 purchase totals =	$954.61		$1,042.7194	$1,042.73	$1,042.70	$1,042.70