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	$210.46	13.484%	$238.8384	$238.84	$238.85	$238.80
Purchase #2	$108.96	4.329%	$113.6769	$113.68	$113.70	$113.70
Purchase #3	$114.75	7.406%	$123.2484	$123.25	$123.25	$123.20
Purchase #4	$34.79	6.480%	$37.0444	$37.04	$37.05	$37.00
Purchase #5	$24.79	4.299%	$25.8557	$25.86	$25.85	$25.90
Purchase #6	$210.55	7.255%	$225.8254	$225.83	$225.85	$225.80
Purchase #7	$229.39	3.864%	$238.2536	$238.25	$238.25	$238.30
7 purchase totals =	$933.69		$1,002.7428	$1,002.75	$1,002.80	$1,002.70