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	$202.30	10.475%	$223.4909	$223.49	$223.50	$223.50
Purchase #2	$108.38	12.153%	$121.5514	$121.55	$121.55	$121.60
Purchase #3	$84.67	9.258%	$92.5087	$92.51	$92.50	$92.50
Purchase #4	$138.77	5.590%	$146.5272	$146.53	$146.55	$146.50
Purchase #5	$196.69	5.776%	$208.0508	$208.05	$208.05	$208.10
Purchase #6	$213.48	5.544%	$225.3153	$225.32	$225.30	$225.30
Purchase #7	$123.37	8.230%	$133.5234	$133.52	$133.50	$133.50
7 purchase totals =	$1,067.66		$1,150.9677	$1,150.97	$1,150.95	$1,151.00