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	$215.38	10.166%	$237.2755	$237.28	$237.30	$237.30
Purchase #2	$136.43	3.218%	$140.8203	$140.82	$140.80	$140.80
Purchase #3	$178.59	7.835%	$192.5825	$192.58	$192.60	$192.60
Purchase #4	$73.39	6.773%	$78.3607	$78.36	$78.35	$78.40
Purchase #5	$49.27	4.103%	$51.2915	$51.29	$51.30	$51.30
Purchase #6	$65.50	8.479%	$71.0537	$71.05	$71.05	$71.10
Purchase #7	$246.87	5.517%	$260.4898	$260.49	$260.50	$260.50
7 purchase totals =	$965.43		$1,031.8740	$1,031.87	$1,031.90	$1,032.00