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	$166.59	7.753%	$179.5057	$179.51	$179.50	$179.50
Purchase #2	$217.35	7.358%	$233.3426	$233.34	$233.35	$233.30
Purchase #3	$61.42	8.212%	$66.4638	$66.46	$66.45	$66.50
Purchase #4	$35.83	8.373%	$38.83	$38.83	$38.85	$38.80
Purchase #5	$168.59	9.783%	$185.0832	$185.08	$185.10	$185.10
Purchase #6	$140.32	3.591%	$145.3589	$145.36	$145.35	$145.40
Purchase #7	$243.26	11.775%	$271.9039	$271.90	$271.90	$271.90
7 purchase totals =	$1,033.36		$1,120.4881	$1,120.48	$1,120.50	$1,120.50