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	$233.88	12.541%	$263.2109	$263.21	$263.20	$263.20
Purchase #2	$102.86	13.549%	$116.7965	$116.80	$116.80	$116.80
Purchase #3	$51.52	5.299%	$54.25	$54.25	$54.25	$54.30
Purchase #4	$41.94	11.604%	$46.8067	$46.81	$46.80	$46.80
Purchase #5	$231.40	13.756%	$263.2314	$263.23	$263.25	$263.20
Purchase #6	$77.69	10.498%	$85.8459	$85.85	$85.85	$85.80
Purchase #7	$249.35	6.761%	$266.2086	$266.21	$266.20	$266.20
7 purchase totals =	$988.64		$1,096.3500	$1,096.36	$1,096.35	$1,096.30