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	$232.28	12.312%	$260.8783	$260.88	$260.90	$260.90
Purchase #2	$28.69	3.128%	$29.5874	$29.59	$29.60	$29.60
Purchase #3	$113.27	3.159%	$116.8482	$116.85	$116.85	$116.80
Purchase #4	$90.79	9.531%	$99.4432	$99.44	$99.45	$99.40
Purchase #5	$62.91	4.419%	$65.69	$65.69	$65.70	$65.70
Purchase #6	$242.69	5.809%	$256.7879	$256.79	$256.80	$256.80
Purchase #7	$94.86	8.713%	$103.1252	$103.13	$103.15	$103.10
7 purchase totals =	$865.49		$932.3602	$932.37	$932.45	$932.30