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	$234.80	11.784%	$262.4688	$262.47	$262.45	$262.50
Purchase #2	$115.91	8.188%	$125.4007	$125.40	$125.40	$125.40
Purchase #3	$49.47	12.725%	$55.7651	$55.77	$55.75	$55.80
Purchase #4	$55.26	7.463%	$59.3841	$59.38	$59.40	$59.40
Purchase #5	$215.79	8.758%	$234.6889	$234.69	$234.70	$234.70
Purchase #6	$42.51	6.463%	$45.2574	$45.26	$45.25	$45.30
Purchase #7	$203.82	9.646%	$223.4805	$223.48	$223.50	$223.50
7 purchase totals =	$917.56		$1,006.4455	$1,006.45	$1,006.45	$1,006.60