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	$100.49	3.759%	$104.2674	$104.27	$104.25	$104.30
Purchase #2	$124.34	13.373%	$140.968	$140.97	$140.95	$141.00
Purchase #3	$240.38	6.185%	$255.2475	$255.25	$255.25	$255.20
Purchase #4	$222.92	8.499%	$241.866	$241.87	$241.85	$241.90
Purchase #5	$250.71	4.682%	$262.4482	$262.45	$262.45	$262.40
Purchase #6	$5.99	4.695%	$6.2712	$6.27	$6.25	$6.30
Purchase #7	$197.62	7.730%	$212.896	$212.90	$212.90	$212.90
7 purchase totals =	$1,142.45		$1,223.9643	$1,223.98	$1,223.90	$1,224.00