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	$242.98	12.541%	$273.4521	$273.45	$273.45	$273.50
Purchase #2	$9.30	12.536%	$10.4658	$10.47	$10.45	$10.50
Purchase #3	$232.97	6.854%	$248.9378	$248.94	$248.95	$248.90
Purchase #4	$241.90	10.494%	$267.285	$267.29	$267.30	$267.30
Purchase #5	$96.98	13.311%	$109.889	$109.89	$109.90	$109.90
Purchase #6	$33.28	13.671%	$37.8297	$37.83	$37.85	$37.80
Purchase #7	$177.65	9.548%	$194.612	$194.61	$194.60	$194.60
7 purchase totals =	$1,035.06		$1,142.4714	$1,142.48	$1,142.50	$1,142.50