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	$75.81	12.769%	$85.4902	$85.49	$85.50	$85.50
Purchase #2	$184.92	12.617%	$208.2514	$208.25	$208.25	$208.30
Purchase #3	$13.42	12.777%	$15.1347	$15.13	$15.15	$15.10
Purchase #4	$223.52	3.755%	$231.9132	$231.91	$231.90	$231.90
Purchase #5	$246.76	3.513%	$255.4287	$255.43	$255.45	$255.40
Purchase #6	$133.29	13.758%	$151.628	$151.63	$151.65	$151.60
Purchase #7	$95.77	10.336%	$105.6688	$105.67	$105.65	$105.70
7 purchase totals =	$973.49		$1,053.5150	$1,053.51	$1,053.55	$1,053.50