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	$117.28	7.637%	$126.2367	$126.24	$126.25	$126.20
Purchase #2	$238.60	6.630%	$254.4192	$254.42	$254.40	$254.40
Purchase #3	$148.33	9.775%	$162.8293	$162.83	$162.85	$162.80
Purchase #4	$136.98	3.324%	$141.5332	$141.53	$141.55	$141.50
Purchase #5	$175.96	6.734%	$187.8091	$187.81	$187.80	$187.80
Purchase #6	$104.76	7.339%	$112.4483	$112.45	$112.45	$112.40
Purchase #7	$182.79	7.707%	$196.8776	$196.88	$196.90	$196.90
7 purchase totals =	$1,104.70		$1,182.1534	$1,182.16	$1,182.20	$1,182.00