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	$206.61	9.167%	$225.5499	$225.55	$225.55	$225.50
Purchase #2	$142.39	6.726%	$151.9672	$151.97	$151.95	$152.00
Purchase #3	$119.27	3.252%	$123.1487	$123.15	$123.15	$123.10
Purchase #4	$86.52	5.683%	$91.4369	$91.44	$91.45	$91.40
Purchase #5	$114.81	7.860%	$123.8341	$123.83	$123.85	$123.80
Purchase #6	$54.40	11.541%	$60.6783	$60.68	$60.70	$60.70
Purchase #7	$66.99	8.330%	$72.5703	$72.57	$72.55	$72.60
7 purchase totals =	$790.99		$849.1854	$849.19	$849.20	$849.10