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	$244.36	7.403%	$262.45	$262.45	$262.45	$262.50
Purchase #2	$189.66	5.850%	$200.7551	$200.76	$200.75	$200.80
Purchase #3	$37.27	9.548%	$40.8285	$40.83	$40.85	$40.80
Purchase #4	$89.41	7.250%	$95.8922	$95.89	$95.90	$95.90
Purchase #5	$83.54	3.682%	$86.6159	$86.62	$86.60	$86.60
Purchase #6	$180.31	8.802%	$196.1809	$196.18	$196.20	$196.20
Purchase #7	$161.77	9.292%	$176.8017	$176.80	$176.80	$176.80
7 purchase totals =	$986.32		$1,059.5243	$1,059.53	$1,059.55	$1,059.60