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	$32.82	10.747%	$36.3472	$36.35	$36.35	$36.30
Purchase #2	$45.73	12.678%	$51.5276	$51.53	$51.55	$51.50
Purchase #3	$231.88	13.755%	$263.7751	$263.78	$263.80	$263.80
Purchase #4	$118.57	3.121%	$122.2706	$122.27	$122.25	$122.30
Purchase #5	$182.39	12.561%	$205.3	$205.30	$205.30	$205.30
Purchase #6	$206.85	9.185%	$225.8492	$225.85	$225.85	$225.80
Purchase #7	$193.65	6.636%	$206.5006	$206.50	$206.50	$206.50
7 purchase totals =	$1,011.89		$1,111.5703	$1,111.58	$1,111.60	$1,111.50