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	$51.68	10.124%	$56.9121	$56.91	$56.90	$56.90
Purchase #2	$208.83	3.175%	$215.4604	$215.46	$215.45	$215.50
Purchase #3	$170.89	8.782%	$185.8976	$185.90	$185.90	$185.90
Purchase #4	$123.71	6.151%	$131.3194	$131.32	$131.30	$131.30
Purchase #5	$102.51	9.722%	$112.476	$112.48	$112.50	$112.50
Purchase #6	$202.31	8.732%	$219.9757	$219.98	$220.00	$220.00
Purchase #7	$83.48	6.804%	$89.16	$89.16	$89.15	$89.20
7 purchase totals =	$943.41		$1,011.2012	$1,011.21	$1,011.20	$1,011.30