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	$199.43	12.359%	$224.0776	$224.08	$224.10	$224.10
Purchase #2	$201.87	11.732%	$225.5534	$225.55	$225.55	$225.60
Purchase #3	$118.59	8.340%	$128.4804	$128.48	$128.50	$128.50
Purchase #4	$60.28	11.507%	$67.2164	$67.22	$67.20	$67.20
Purchase #5	$105.57	10.110%	$116.2431	$116.24	$116.25	$116.20
Purchase #6	$166.47	12.665%	$187.5534	$187.55	$187.55	$187.60
Purchase #7	$102.86	9.170%	$112.2923	$112.29	$112.30	$112.30
7 purchase totals =	$955.07		$1,061.4166	$1,061.41	$1,061.45	$1,061.50