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	$43.84	9.261%	$47.9	$47.90	$47.90	$47.90
Purchase #2	$176.48	12.521%	$198.5771	$198.58	$198.60	$198.60
Purchase #3	$218.92	13.702%	$248.9164	$248.92	$248.90	$248.90
Purchase #4	$152.49	11.764%	$170.4289	$170.43	$170.45	$170.40
Purchase #5	$133.90	3.473%	$138.5503	$138.55	$138.55	$138.60
Purchase #6	$183.78	13.383%	$208.3753	$208.38	$208.40	$208.40
Purchase #7	$82.25	10.132%	$90.5836	$90.58	$90.60	$90.60
7 purchase totals =	$991.66		$1,103.3316	$1,103.34	$1,103.40	$1,103.40