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	$41.75	7.431%	$44.8524	$44.85	$44.85	$44.90
Purchase #2	$32.56	8.327%	$35.2713	$35.27	$35.25	$35.30
Purchase #3	$58.40	9.222%	$63.7856	$63.79	$63.80	$63.80
Purchase #4	$14.83	3.864%	$15.403	$15.40	$15.40	$15.40
Purchase #5	$54.64	9.639%	$59.9067	$59.91	$59.90	$59.90
Purchase #6	$154.74	7.628%	$166.5436	$166.54	$166.55	$166.50
Purchase #7	$248.83	10.475%	$274.8949	$274.89	$274.90	$274.90
7 purchase totals =	$605.75		$660.6575	$660.65	$660.65	$660.70