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	$183.25	4.792%	$192.0313	$192.03	$192.05	$192.00
Purchase #2	$217.96	10.372%	$240.5668	$240.57	$240.55	$240.60
Purchase #3	$50.84	11.830%	$56.8544	$56.85	$56.85	$56.90
Purchase #4	$88.75	12.217%	$99.5926	$99.59	$99.60	$99.60
Purchase #5	$125.62	12.173%	$140.9117	$140.91	$140.90	$140.90
Purchase #6	$109.65	5.788%	$115.9965	$116.00	$116.00	$116.00
Purchase #7	$113.49	9.209%	$123.9413	$123.94	$123.95	$123.90
7 purchase totals =	$889.56		$969.8946	$969.89	$969.90	$969.90