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	$207.79	3.678%	$215.4325	$215.43	$215.45	$215.40
Purchase #2	$178.98	10.703%	$198.1362	$198.14	$198.15	$198.10
Purchase #3	$63.31	6.727%	$67.5689	$67.57	$67.55	$67.60
Purchase #4	$179.44	9.246%	$196.031	$196.03	$196.05	$196.00
Purchase #5	$111.96	13.335%	$126.8899	$126.89	$126.90	$126.90
Purchase #6	$30.41	11.342%	$33.8591	$33.86	$33.85	$33.90
Purchase #7	$97.29	5.264%	$102.4113	$102.41	$102.40	$102.40
7 purchase totals =	$869.18		$940.3289	$940.33	$940.35	$940.30