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	$114.84	13.208%	$130.0081	$130.01	$130.00	$130.00
Purchase #2	$61.59	8.564%	$66.8646	$66.86	$66.85	$66.90
Purchase #3	$42.66	4.828%	$44.7196	$44.72	$44.70	$44.70
Purchase #4	$81.48	7.791%	$87.8281	$87.83	$87.85	$87.80
Purchase #5	$96.92	13.141%	$109.6563	$109.66	$109.65	$109.70
Purchase #6	$119.80	6.780%	$127.9224	$127.92	$127.90	$127.90
Purchase #7	$127.47	9.870%	$140.0513	$140.05	$140.05	$140.10
7 purchase totals =	$644.76		$707.0504	$707.05	$707.00	$707.10