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	$108.81	13.752%	$123.7736	$123.77	$123.75	$123.80
Purchase #2	$129.86	5.426%	$136.9062	$136.91	$136.90	$136.90
Purchase #3	$193.85	8.817%	$210.9418	$210.94	$210.95	$210.90
Purchase #4	$199.78	11.381%	$222.517	$222.52	$222.50	$222.50
Purchase #5	$48.87	5.659%	$51.6356	$51.64	$51.65	$51.60
Purchase #6	$222.41	8.653%	$241.6551	$241.66	$241.65	$241.70
Purchase #7	$208.72	7.220%	$223.7896	$223.79	$223.80	$223.80
7 purchase totals =	$1,112.30		$1,211.2189	$1,211.23	$1,211.20	$1,211.20