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	$34.71	3.466%	$35.913	$35.91	$35.90	$35.90
Purchase #2	$35.26	11.625%	$39.359	$39.36	$39.35	$39.40
Purchase #3	$87.97	9.315%	$96.1644	$96.16	$96.15	$96.20
Purchase #4	$131.64	4.453%	$137.5019	$137.50	$137.50	$137.50
Purchase #5	$131.56	8.567%	$142.8307	$142.83	$142.85	$142.80
Purchase #6	$182.85	5.504%	$192.9141	$192.91	$192.90	$192.90
Purchase #7	$241.70	5.851%	$255.8419	$255.84	$255.85	$255.80
7 purchase totals =	$845.69		$900.5250	$900.51	$900.50	$900.50