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	$94.80	10.516%	$104.7692	$104.77	$104.75	$104.80
Purchase #2	$94.39	3.579%	$97.7682	$97.77	$97.75	$97.80
Purchase #3	$194.39	11.320%	$216.3949	$216.39	$216.40	$216.40
Purchase #4	$129.52	10.523%	$143.1494	$143.15	$143.15	$143.10
Purchase #5	$26.91	10.754%	$29.8039	$29.80	$29.80	$29.80
Purchase #6	$85.87	13.318%	$97.3062	$97.31	$97.30	$97.30
Purchase #7	$67.83	6.607%	$72.3115	$72.31	$72.30	$72.30
7 purchase totals =	$693.71		$761.5033	$761.50	$761.45	$761.50