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	$169.84	12.397%	$190.8951	$190.90	$190.90	$190.90
Purchase #2	$140.57	9.603%	$154.0689	$154.07	$154.05	$154.10
Purchase #3	$206.59	9.679%	$226.5858	$226.59	$226.60	$226.60
Purchase #4	$84.68	5.427%	$89.2756	$89.28	$89.30	$89.30
Purchase #5	$14.85	5.112%	$15.6091	$15.61	$15.60	$15.60
Purchase #6	$222.64	7.179%	$238.6233	$238.62	$238.60	$238.60
Purchase #7	$153.96	8.384%	$166.868	$166.87	$166.85	$166.90
7 purchase totals =	$993.13		$1,081.9258	$1,081.94	$1,081.90	$1,082.00