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	$227.84	3.239%	$235.2197	$235.22	$235.20	$235.20
Purchase #2	$82.54	3.677%	$85.575	$85.58	$85.60	$85.60
Purchase #3	$202.43	10.103%	$222.8815	$222.88	$222.90	$222.90
Purchase #4	$79.78	11.305%	$88.7991	$88.80	$88.80	$88.80
Purchase #5	$196.64	11.763%	$219.7708	$219.77	$219.75	$219.80
Purchase #6	$131.50	8.342%	$142.4697	$142.47	$142.45	$142.50
Purchase #7	$42.61	12.204%	$47.8101	$47.81	$47.80	$47.80
7 purchase totals =	$963.34		$1,042.5259	$1,042.53	$1,042.50	$1,042.60