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	$213.73	11.127%	$237.5117	$237.51	$237.50	$237.50
Purchase #2	$153.87	10.244%	$169.6324	$169.63	$169.65	$169.60
Purchase #3	$143.56	5.346%	$151.2347	$151.23	$151.25	$151.20
Purchase #4	$44.77	4.397%	$46.7385	$46.74	$46.75	$46.70
Purchase #5	$21.78	12.381%	$24.4766	$24.48	$24.50	$24.50
Purchase #6	$203.63	6.242%	$216.3406	$216.34	$216.35	$216.30
Purchase #7	$174.50	12.324%	$196.0054	$196.01	$196.00	$196.00
7 purchase totals =	$955.84		$1,041.9399	$1,041.94	$1,042.00	$1,041.80