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	$15.26	9.600%	$16.725	$16.73	$16.75	$16.70
Purchase #2	$232.93	5.548%	$245.853	$245.85	$245.85	$245.90
Purchase #3	$51.50	6.789%	$54.9963	$55.00	$55.00	$55.00
Purchase #4	$8.45	10.155%	$9.3081	$9.31	$9.30	$9.30
Purchase #5	$84.75	6.738%	$90.4605	$90.46	$90.45	$90.50
Purchase #6	$83.73	6.342%	$89.0402	$89.04	$89.05	$89.00
Purchase #7	$151.55	3.541%	$156.9164	$156.92	$156.90	$156.90
7 purchase totals =	$628.17		$663.2995	$663.31	$663.30	$663.30