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	$48.40	8.217%	$52.377	$52.38	$52.40	$52.40
Purchase #2	$150.95	13.534%	$171.3796	$171.38	$171.40	$171.40
Purchase #3	$200.92	8.107%	$217.2086	$217.21	$217.20	$217.20
Purchase #4	$227.38	3.529%	$235.4042	$235.40	$235.40	$235.40
Purchase #5	$148.92	5.383%	$156.9364	$156.94	$156.95	$156.90
Purchase #6	$138.74	9.453%	$151.8551	$151.86	$151.85	$151.90
Purchase #7	$67.27	7.719%	$72.4626	$72.46	$72.45	$72.50
7 purchase totals =	$982.58		$1,057.6235	$1,057.63	$1,057.65	$1,057.70