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	$246.85	7.684%	$265.818	$265.82	$265.80	$265.80
Purchase #2	$187.77	6.447%	$199.8755	$199.88	$199.90	$199.90
Purchase #3	$87.54	6.296%	$93.0515	$93.05	$93.05	$93.10
Purchase #4	$237.87	12.672%	$268.0129	$268.01	$268.00	$268.00
Purchase #5	$20.77	3.464%	$21.4895	$21.49	$21.50	$21.50
Purchase #6	$37.25	3.466%	$38.5411	$38.54	$38.55	$38.50
Purchase #7	$196.82	5.105%	$206.8677	$206.87	$206.85	$206.90
7 purchase totals =	$1,014.87		$1,093.6562	$1,093.66	$1,093.65	$1,093.70