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	$213.71	10.234%	$235.5811	$235.58	$235.60	$235.60
Purchase #2	$122.96	3.660%	$127.4603	$127.46	$127.45	$127.50
Purchase #3	$217.81	11.582%	$243.0368	$243.04	$243.05	$243.00
Purchase #4	$165.49	6.690%	$176.5613	$176.56	$176.55	$176.60
Purchase #5	$219.95	5.754%	$232.6059	$232.61	$232.60	$232.60
Purchase #6	$98.37	5.147%	$103.4331	$103.43	$103.45	$103.40
Purchase #7	$29.61	6.673%	$31.5859	$31.59	$31.60	$31.60
7 purchase totals =	$1,067.90		$1,150.2644	$1,150.27	$1,150.30	$1,150.30