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	$53.93	8.139%	$58.3194	$58.32	$58.30	$58.30
Purchase #2	$184.34	5.702%	$194.8511	$194.85	$194.85	$194.90
Purchase #3	$72.32	5.475%	$76.2795	$76.28	$76.30	$76.30
Purchase #4	$188.35	4.219%	$196.2965	$196.30	$196.30	$196.30
Purchase #5	$40.43	7.610%	$43.5067	$43.51	$43.50	$43.50
Purchase #6	$213.43	3.749%	$221.4315	$221.43	$221.45	$221.40
Purchase #7	$205.65	5.761%	$217.4975	$217.50	$217.50	$217.50
7 purchase totals =	$958.45		$1,008.1822	$1,008.19	$1,008.20	$1,008.20