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	$175.66	13.279%	$198.9859	$198.99	$199.00	$199.00
Purchase #2	$75.57	12.807%	$85.2482	$85.25	$85.25	$85.20
Purchase #3	$156.97	9.754%	$172.2809	$172.28	$172.30	$172.30
Purchase #4	$125.39	5.616%	$132.4319	$132.43	$132.45	$132.40
Purchase #5	$59.88	12.675%	$67.4698	$67.47	$67.45	$67.50
Purchase #6	$146.45	12.594%	$164.8939	$164.89	$164.90	$164.90
Purchase #7	$155.66	13.425%	$176.5574	$176.56	$176.55	$176.60
7 purchase totals =	$895.58		$997.8680	$997.87	$997.90	$997.90