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	$104.78	4.438%	$109.4301	$109.43	$109.45	$109.40
Purchase #2	$14.25	9.674%	$15.6285	$15.63	$15.65	$15.60
Purchase #3	$247.49	4.446%	$258.4934	$258.49	$258.50	$258.50
Purchase #4	$49.96	12.124%	$56.0172	$56.02	$56.00	$56.00
Purchase #5	$46.37	11.270%	$51.5959	$51.60	$51.60	$51.60
Purchase #6	$102.44	5.208%	$107.7751	$107.78	$107.80	$107.80
Purchase #7	$185.82	5.730%	$196.4675	$196.47	$196.45	$196.50
7 purchase totals =	$751.11		$795.4077	$795.42	$795.45	$795.40