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	$209.92	8.254%	$227.2468	$227.25	$227.25	$227.20
Purchase #2	$130.70	6.186%	$138.7851	$138.79	$138.80	$138.80
Purchase #3	$164.52	3.219%	$169.8159	$169.82	$169.80	$169.80
Purchase #4	$103.51	8.466%	$112.2732	$112.27	$112.25	$112.30
Purchase #5	$247.27	3.453%	$255.8082	$255.81	$255.80	$255.80
Purchase #6	$220.57	9.215%	$240.8955	$240.90	$240.90	$240.90
Purchase #7	$237.92	7.841%	$256.5753	$256.58	$256.60	$256.60
7 purchase totals =	$1,314.41		$1,401.4000	$1,401.42	$1,401.40	$1,401.40