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	$36.37	5.537%	$38.3838	$38.38	$38.40	$38.40
Purchase #2	$243.55	4.115%	$253.5721	$253.57	$253.55	$253.60
Purchase #3	$192.85	6.562%	$205.5048	$205.50	$205.50	$205.50
Purchase #4	$6.25	9.630%	$6.8519	$6.85	$6.85	$6.90
Purchase #5	$189.59	13.508%	$215.1998	$215.20	$215.20	$215.20
Purchase #6	$113.89	8.541%	$123.6173	$123.62	$123.60	$123.60
Purchase #7	$234.39	11.688%	$261.7855	$261.79	$261.80	$261.80
7 purchase totals =	$1,016.89		$1,104.9152	$1,104.91	$1,104.90	$1,105.00