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	$117.29	8.384%	$127.1236	$127.12	$127.10	$127.10
Purchase #2	$30.34	10.293%	$33.4629	$33.46	$33.45	$33.50
Purchase #3	$118.25	7.374%	$126.9698	$126.97	$126.95	$127.00
Purchase #4	$46.73	8.123%	$50.5259	$50.53	$50.55	$50.50
Purchase #5	$28.59	9.746%	$31.3764	$31.38	$31.40	$31.40
Purchase #6	$144.95	5.807%	$153.3672	$153.37	$153.35	$153.40
Purchase #7	$81.48	7.504%	$87.5943	$87.59	$87.60	$87.60
7 purchase totals =	$567.63		$610.4201	$610.42	$610.40	$610.50