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	$170.88	12.617%	$192.4399	$192.44	$192.45	$192.40
Purchase #2	$30.86	6.192%	$32.7709	$32.77	$32.75	$32.80
Purchase #3	$39.66	9.620%	$43.4753	$43.48	$43.50	$43.50
Purchase #4	$82.77	5.771%	$87.5467	$87.55	$87.55	$87.50
Purchase #5	$238.44	7.393%	$256.0679	$256.07	$256.05	$256.10
Purchase #6	$167.69	10.609%	$185.4802	$185.48	$185.50	$185.50
Purchase #7	$29.84	5.609%	$31.5137	$31.51	$31.50	$31.50
7 purchase totals =	$760.14		$829.2946	$829.30	$829.30	$829.30