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	$46.25	4.790%	$48.4654	$48.47	$48.45	$48.50
Purchase #2	$93.63	7.299%	$100.4641	$100.46	$100.45	$100.50
Purchase #3	$19.78	3.516%	$20.4755	$20.48	$20.50	$20.50
Purchase #4	$127.34	4.800%	$133.4523	$133.45	$133.45	$133.50
Purchase #5	$214.53	10.212%	$236.4378	$236.44	$236.45	$236.40
Purchase #6	$77.53	11.725%	$86.6204	$86.62	$86.60	$86.60
Purchase #7	$180.34	10.321%	$198.9529	$198.95	$198.95	$199.00
7 purchase totals =	$759.40		$824.8684	$824.87	$824.85	$825.00