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	$152.54	10.574%	$168.6696	$168.67	$168.65	$168.70
Purchase #2	$115.83	13.527%	$131.4983	$131.50	$131.50	$131.50
Purchase #3	$143.54	11.820%	$160.5064	$160.51	$160.50	$160.50
Purchase #4	$22.96	10.400%	$25.3478	$25.35	$25.35	$25.30
Purchase #5	$147.89	13.210%	$167.4263	$167.43	$167.45	$167.40
Purchase #6	$180.85	6.694%	$192.9561	$192.96	$192.95	$193.00
Purchase #7	$75.26	3.543%	$77.9265	$77.93	$77.95	$77.90
7 purchase totals =	$838.87		$924.3310	$924.35	$924.35	$924.30