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	$82.82	12.379%	$93.0723	$93.07	$93.05	$93.10
Purchase #2	$228.35	9.493%	$250.0273	$250.03	$250.05	$250.00
Purchase #3	$9.67	12.757%	$10.9036	$10.90	$10.90	$10.90
Purchase #4	$184.97	9.674%	$202.864	$202.86	$202.85	$202.90
Purchase #5	$129.83	11.695%	$145.0136	$145.01	$145.00	$145.00
Purchase #6	$106.44	5.307%	$112.0888	$112.09	$112.10	$112.10
Purchase #7	$104.81	6.754%	$111.8889	$111.89	$111.90	$111.90
7 purchase totals =	$846.89		$925.8585	$925.85	$925.85	$925.90