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	$206.43	4.448%	$215.612	$215.61	$215.60	$215.60
Purchase #2	$43.51	11.536%	$48.5293	$48.53	$48.55	$48.50
Purchase #3	$243.79	7.726%	$262.6252	$262.63	$262.65	$262.60
Purchase #4	$215.92	6.289%	$229.4992	$229.50	$229.50	$229.50
Purchase #5	$41.65	8.595%	$45.2298	$45.23	$45.25	$45.20
Purchase #6	$210.46	12.835%	$237.4725	$237.47	$237.45	$237.50
Purchase #7	$31.72	4.508%	$33.1499	$33.15	$33.15	$33.10
7 purchase totals =	$993.48		$1,072.1179	$1,072.12	$1,072.15	$1,072.00