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	$131.89	8.360%	$142.916	$142.92	$142.90	$142.90
Purchase #2	$52.83	12.675%	$59.5262	$59.53	$59.55	$59.50
Purchase #3	$101.61	8.592%	$110.3403	$110.34	$110.35	$110.30
Purchase #4	$49.61	4.479%	$51.832	$51.83	$51.85	$51.80
Purchase #5	$180.84	8.452%	$196.1246	$196.12	$196.10	$196.10
Purchase #6	$10.81	9.393%	$11.8254	$11.83	$11.85	$11.80
Purchase #7	$144.83	11.766%	$161.8707	$161.87	$161.85	$161.90
7 purchase totals =	$672.42		$734.4352	$734.44	$734.45	$734.30