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	$65.95	11.147%	$73.3014	$73.30	$73.30	$73.30
Purchase #2	$189.50	10.501%	$209.3994	$209.40	$209.40	$209.40
Purchase #3	$137.48	4.330%	$143.4329	$143.43	$143.45	$143.40
Purchase #4	$35.46	9.339%	$38.7716	$38.77	$38.75	$38.80
Purchase #5	$39.90	8.684%	$43.3649	$43.36	$43.35	$43.40
Purchase #6	$80.97	12.301%	$90.9301	$90.93	$90.95	$90.90
Purchase #7	$171.72	8.811%	$186.8502	$186.85	$186.85	$186.90
7 purchase totals =	$720.98		$786.0505	$786.04	$786.05	$786.10