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	$58.97	8.351%	$63.8946	$63.89	$63.90	$63.90
Purchase #2	$38.89	5.259%	$40.9352	$40.94	$40.95	$40.90
Purchase #3	$23.82	12.817%	$26.873	$26.87	$26.85	$26.90
Purchase #4	$89.59	8.231%	$96.9642	$96.96	$96.95	$97.00
Purchase #5	$138.66	7.323%	$148.8141	$148.81	$148.80	$148.80
Purchase #6	$68.47	4.543%	$71.5806	$71.58	$71.60	$71.60
Purchase #7	$180.79	8.699%	$196.5169	$196.52	$196.50	$196.50
7 purchase totals =	$599.19		$645.5786	$645.57	$645.55	$645.60