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	$13.63	3.587%	$14.1189	$14.12	$14.10	$14.10
Purchase #2	$224.78	6.388%	$239.1389	$239.14	$239.15	$239.10
Purchase #3	$43.84	6.136%	$46.53	$46.53	$46.55	$46.50
Purchase #4	$124.78	11.458%	$139.0773	$139.08	$139.10	$139.10
Purchase #5	$117.31	7.290%	$125.8619	$125.86	$125.85	$125.90
Purchase #6	$85.95	5.167%	$90.391	$90.39	$90.40	$90.40
Purchase #7	$249.92	12.389%	$280.8826	$280.88	$280.90	$280.90
7 purchase totals =	$860.21		$936.0006	$936.00	$936.05	$936.00