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	$203.29	9.414%	$222.4277	$222.43	$222.45	$222.40
Purchase #2	$107.73	5.395%	$113.542	$113.54	$113.55	$113.50
Purchase #3	$25.56	11.545%	$28.5109	$28.51	$28.50	$28.50
Purchase #4	$149.81	4.446%	$156.4706	$156.47	$156.45	$156.50
Purchase #5	$223.74	6.480%	$238.2384	$238.24	$238.25	$238.20
Purchase #6	$182.82	5.441%	$192.7672	$192.77	$192.75	$192.80
Purchase #7	$146.39	10.577%	$161.8737	$161.87	$161.85	$161.90
7 purchase totals =	$1,039.34		$1,113.8305	$1,113.83	$1,113.80	$1,113.80