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	$80.61	10.202%	$88.8338	$88.83	$88.85	$88.80
Purchase #2	$11.34	13.347%	$12.8535	$12.85	$12.85	$12.90
Purchase #3	$228.65	8.660%	$248.4511	$248.45	$248.45	$248.50
Purchase #4	$119.35	10.143%	$131.4557	$131.46	$131.45	$131.50
Purchase #5	$145.91	9.337%	$159.5336	$159.53	$159.55	$159.50
Purchase #6	$227.48	12.753%	$256.4905	$256.49	$256.50	$256.50
Purchase #7	$249.92	7.768%	$269.3338	$269.33	$269.35	$269.30
7 purchase totals =	$1,063.26		$1,166.9520	$1,166.94	$1,167.00	$1,167.00