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	$78.25	10.793%	$86.6955	$86.70	$86.70	$86.70
Purchase #2	$154.44	3.178%	$159.3481	$159.35	$159.35	$159.30
Purchase #3	$37.83	12.529%	$42.5697	$42.57	$42.55	$42.60
Purchase #4	$152.79	7.667%	$164.5044	$164.50	$164.50	$164.50
Purchase #5	$241.49	7.438%	$259.452	$259.45	$259.45	$259.50
Purchase #6	$210.38	4.359%	$219.5505	$219.55	$219.55	$219.60
Purchase #7	$7.53	5.542%	$7.9473	$7.95	$7.95	$7.90
7 purchase totals =	$882.71		$940.0675	$940.07	$940.05	$940.10