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	$24.57	5.325%	$25.8784	$25.88	$25.90	$25.90
Purchase #2	$84.89	6.646%	$90.5318	$90.53	$90.55	$90.50
Purchase #3	$43.37	5.254%	$45.6487	$45.65	$45.65	$45.60
Purchase #4	$186.55	7.381%	$200.3193	$200.32	$200.30	$200.30
Purchase #5	$129.49	4.223%	$134.9584	$134.96	$134.95	$135.00
Purchase #6	$76.73	9.392%	$83.9365	$83.94	$83.95	$83.90
Purchase #7	$161.63	8.499%	$175.3669	$175.37	$175.35	$175.40
7 purchase totals =	$707.23		$756.6400	$756.65	$756.65	$756.60