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	$186.76	11.215%	$207.7051	$207.71	$207.70	$207.70
Purchase #2	$249.61	6.314%	$265.3704	$265.37	$265.35	$265.40
Purchase #3	$75.45	3.709%	$78.2484	$78.25	$78.25	$78.20
Purchase #4	$126.42	11.587%	$141.0683	$141.07	$141.05	$141.10
Purchase #5	$203.43	6.137%	$215.9145	$215.91	$215.90	$215.90
Purchase #6	$54.90	12.442%	$61.7307	$61.73	$61.75	$61.70
Purchase #7	$164.58	4.193%	$171.4808	$171.48	$171.50	$171.50
7 purchase totals =	$1,061.15		$1,141.5182	$1,141.52	$1,141.50	$1,141.50