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	$144.86	10.189%	$159.6198	$159.62	$159.60	$159.60
Purchase #2	$186.38	12.580%	$209.8266	$209.83	$209.85	$209.80
Purchase #3	$208.49	4.802%	$218.5017	$218.50	$218.50	$218.50
Purchase #4	$87.84	10.390%	$96.9666	$96.97	$96.95	$97.00
Purchase #5	$217.27	13.359%	$246.2951	$246.30	$246.30	$246.30
Purchase #6	$62.65	13.691%	$71.2274	$71.23	$71.25	$71.20
Purchase #7	$55.36	11.639%	$61.8034	$61.80	$61.80	$61.80
7 purchase totals =	$962.85		$1,064.2406	$1,064.25	$1,064.25	$1,064.20