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	$133.90	9.275%	$146.3192	$146.32	$146.30	$146.30
Purchase #2	$103.47	13.382%	$117.3164	$117.32	$117.30	$117.30
Purchase #3	$233.44	12.349%	$262.2675	$262.27	$262.25	$262.30
Purchase #4	$56.72	4.826%	$59.4573	$59.46	$59.45	$59.50
Purchase #5	$217.64	12.390%	$244.6056	$244.61	$244.60	$244.60
Purchase #6	$37.58	9.859%	$41.285	$41.29	$41.30	$41.30
Purchase #7	$9.74	5.478%	$10.2736	$10.27	$10.25	$10.30
7 purchase totals =	$792.49		$881.5246	$881.54	$881.45	$881.60