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	$9.60	9.265%	$10.4894	$10.49	$10.50	$10.50
Purchase #2	$174.98	12.238%	$196.3941	$196.39	$196.40	$196.40
Purchase #3	$158.84	3.550%	$164.4788	$164.48	$164.50	$164.50
Purchase #4	$188.75	4.184%	$196.6473	$196.65	$196.65	$196.60
Purchase #5	$41.46	7.400%	$44.528	$44.53	$44.55	$44.50
Purchase #6	$122.51	9.497%	$134.1448	$134.14	$134.15	$134.10
Purchase #7	$62.35	4.870%	$65.3864	$65.39	$65.40	$65.40
7 purchase totals =	$758.49		$812.0688	$812.07	$812.15	$812.00