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	$218.81	11.871%	$244.7849	$244.78	$244.80	$244.80
Purchase #2	$131.61	9.521%	$144.1406	$144.14	$144.15	$144.10
Purchase #3	$82.58	8.853%	$89.8908	$89.89	$89.90	$89.90
Purchase #4	$174.40	7.326%	$187.1765	$187.18	$187.20	$187.20
Purchase #5	$232.57	9.629%	$254.9642	$254.96	$254.95	$255.00
Purchase #6	$205.95	5.157%	$216.5708	$216.57	$216.55	$216.60
Purchase #7	$147.25	9.383%	$161.0665	$161.07	$161.05	$161.10
7 purchase totals =	$1,193.17		$1,298.5943	$1,298.59	$1,298.60	$1,298.70