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	$208.76	9.510%	$228.6131	$228.61	$228.60	$228.60
Purchase #2	$32.43	12.849%	$36.5969	$36.60	$36.60	$36.60
Purchase #3	$73.43	13.490%	$83.3357	$83.34	$83.35	$83.30
Purchase #4	$24.77	11.189%	$27.5415	$27.54	$27.55	$27.50
Purchase #5	$95.71	13.666%	$108.7897	$108.79	$108.80	$108.80
Purchase #6	$41.93	8.678%	$45.5687	$45.57	$45.55	$45.60
Purchase #7	$110.92	11.268%	$123.4185	$123.42	$123.40	$123.40
7 purchase totals =	$587.95		$653.8641	$653.87	$653.85	$653.80