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	$231.25	13.197%	$261.7681	$261.77	$261.75	$261.80
Purchase #2	$57.56	7.735%	$62.0123	$62.01	$62.00	$62.00
Purchase #3	$90.61	7.434%	$97.3459	$97.35	$97.35	$97.30
Purchase #4	$176.82	5.454%	$186.4638	$186.46	$186.45	$186.50
Purchase #5	$244.29	10.734%	$270.5121	$270.51	$270.50	$270.50
Purchase #6	$80.43	11.296%	$89.5154	$89.52	$89.50	$89.50
Purchase #7	$89.94	5.588%	$94.9658	$94.97	$94.95	$95.00
7 purchase totals =	$970.90		$1,062.5834	$1,062.59	$1,062.50	$1,062.60