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	$78.34	9.386%	$85.693	$85.69	$85.70	$85.70
Purchase #2	$43.76	10.331%	$48.2808	$48.28	$48.30	$48.30
Purchase #3	$95.45	8.206%	$103.2826	$103.28	$103.30	$103.30
Purchase #4	$235.71	11.534%	$262.8968	$262.90	$262.90	$262.90
Purchase #5	$115.76	13.359%	$131.2244	$131.22	$131.20	$131.20
Purchase #6	$25.75	5.784%	$27.2394	$27.24	$27.25	$27.20
Purchase #7	$248.94	9.739%	$273.1843	$273.18	$273.20	$273.20
7 purchase totals =	$843.71		$931.8013	$931.79	$931.85	$931.80