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	$218.45	7.800%	$235.4891	$235.49	$235.50	$235.50
Purchase #2	$127.73	4.870%	$133.9505	$133.95	$133.95	$134.00
Purchase #3	$156.77	11.540%	$174.8613	$174.86	$174.85	$174.90
Purchase #4	$112.75	3.265%	$116.4313	$116.43	$116.45	$116.40
Purchase #5	$23.57	4.320%	$24.5882	$24.59	$24.60	$24.60
Purchase #6	$64.26	10.843%	$71.2277	$71.23	$71.25	$71.20
Purchase #7	$241.56	13.643%	$274.516	$274.52	$274.50	$274.50
7 purchase totals =	$945.09		$1,031.0641	$1,031.07	$1,031.10	$1,031.10