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	$60.42	5.744%	$63.8905	$63.89	$63.90	$63.90
Purchase #2	$65.38	5.458%	$68.9484	$68.95	$68.95	$68.90
Purchase #3	$173.92	13.540%	$197.4688	$197.47	$197.45	$197.50
Purchase #4	$87.98	12.325%	$98.8235	$98.82	$98.80	$98.80
Purchase #5	$80.57	11.184%	$89.5809	$89.58	$89.60	$89.60
Purchase #6	$76.54	6.508%	$81.5212	$81.52	$81.50	$81.50
Purchase #7	$51.38	4.582%	$53.7342	$53.73	$53.75	$53.70
7 purchase totals =	$596.19		$653.9675	$653.96	$653.95	$653.90