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	$126.75	13.566%	$143.9449	$143.94	$143.95	$143.90
Purchase #2	$181.48	3.487%	$187.8082	$187.81	$187.80	$187.80
Purchase #3	$52.68	4.281%	$54.9352	$54.94	$54.95	$54.90
Purchase #4	$81.54	9.408%	$89.2113	$89.21	$89.20	$89.20
Purchase #5	$207.77	4.822%	$217.7887	$217.79	$217.80	$217.80
Purchase #6	$33.48	8.679%	$36.3857	$36.39	$36.40	$36.40
Purchase #7	$241.74	12.478%	$271.9043	$271.90	$271.90	$271.90
7 purchase totals =	$925.44		$1,001.9783	$1,001.98	$1,002.00	$1,001.90