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	$193.50	7.639%	$208.2815	$208.28	$208.30	$208.30
Purchase #2	$38.28	12.387%	$43.0217	$43.02	$43.00	$43.00
Purchase #3	$124.78	13.785%	$141.9809	$141.98	$142.00	$142.00
Purchase #4	$55.53	12.200%	$62.3047	$62.30	$62.30	$62.30
Purchase #5	$234.36	11.559%	$261.4497	$261.45	$261.45	$261.40
Purchase #6	$228.52	9.788%	$250.8875	$250.89	$250.90	$250.90
Purchase #7	$54.74	10.449%	$60.4598	$60.46	$60.45	$60.50
7 purchase totals =	$929.71		$1,028.3858	$1,028.38	$1,028.40	$1,028.40