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	$48.52	9.681%	$53.2172	$53.22	$53.20	$53.20
Purchase #2	$199.60	5.141%	$209.8614	$209.86	$209.85	$209.90
Purchase #3	$225.36	11.193%	$250.5845	$250.58	$250.60	$250.60
Purchase #4	$184.33	11.377%	$205.3012	$205.30	$205.30	$205.30
Purchase #5	$125.58	12.196%	$140.8957	$140.90	$140.90	$140.90
Purchase #6	$208.72	11.744%	$233.2321	$233.23	$233.25	$233.20
Purchase #7	$119.56	10.611%	$132.2465	$132.25	$132.25	$132.20
7 purchase totals =	$1,111.67		$1,225.3386	$1,225.34	$1,225.35	$1,225.30