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	$131.96	5.493%	$139.2086	$139.21	$139.20	$139.20
Purchase #2	$210.71	13.516%	$239.1896	$239.19	$239.20	$239.20
Purchase #3	$136.91	10.735%	$151.6073	$151.61	$151.60	$151.60
Purchase #4	$224.31	10.722%	$248.3605	$248.36	$248.35	$248.40
Purchase #5	$40.28	7.508%	$43.3042	$43.30	$43.30	$43.30
Purchase #6	$132.79	3.799%	$137.8347	$137.83	$137.85	$137.80
Purchase #7	$136.57	11.640%	$152.4667	$152.47	$152.45	$152.50
7 purchase totals =	$1,013.53		$1,111.9716	$1,111.97	$1,111.95	$1,112.00