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	$219.41	8.189%	$237.3775	$237.38	$237.40	$237.40
Purchase #2	$94.45	12.108%	$105.886	$105.89	$105.90	$105.90
Purchase #3	$43.48	13.558%	$49.375	$49.38	$49.40	$49.40
Purchase #4	$237.50	5.536%	$250.648	$250.65	$250.65	$250.60
Purchase #5	$77.37	12.414%	$86.9747	$86.97	$86.95	$87.00
Purchase #6	$220.46	4.864%	$231.1832	$231.18	$231.20	$231.20
Purchase #7	$45.49	5.281%	$47.8923	$47.89	$47.90	$47.90
7 purchase totals =	$938.16		$1,009.3367	$1,009.34	$1,009.40	$1,009.40