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	$94.25	9.792%	$103.479	$103.48	$103.50	$103.50
Purchase #2	$86.97	4.205%	$90.6271	$90.63	$90.65	$90.60
Purchase #3	$76.99	8.387%	$83.4472	$83.45	$83.45	$83.40
Purchase #4	$167.66	13.788%	$190.777	$190.78	$190.80	$190.80
Purchase #5	$210.97	9.718%	$231.4721	$231.47	$231.45	$231.50
Purchase #6	$238.64	5.556%	$251.8988	$251.90	$251.90	$251.90
Purchase #7	$29.36	7.255%	$31.4901	$31.49	$31.50	$31.50
7 purchase totals =	$904.84		$983.1913	$983.20	$983.25	$983.20