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	$155.40	13.166%	$175.86	$175.86	$175.85	$175.90
Purchase #2	$161.57	3.405%	$167.0715	$167.07	$167.05	$167.10
Purchase #3	$62.58	4.517%	$65.4067	$65.41	$65.40	$65.40
Purchase #4	$213.71	9.753%	$234.5531	$234.55	$234.55	$234.60
Purchase #5	$208.65	10.752%	$231.084	$231.08	$231.10	$231.10
Purchase #6	$43.61	11.578%	$48.6592	$48.66	$48.65	$48.70
Purchase #7	$101.50	7.399%	$109.01	$109.01	$109.00	$109.00
7 purchase totals =	$947.02		$1,031.6445	$1,031.64	$1,031.60	$1,031.80