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	$116.38	6.567%	$124.0227	$124.02	$124.00	$124.00
Purchase #2	$239.50	6.706%	$255.5609	$255.56	$255.55	$255.60
Purchase #3	$163.27	10.527%	$180.4574	$180.46	$180.45	$180.50
Purchase #4	$34.85	11.663%	$38.9146	$38.91	$38.90	$38.90
Purchase #5	$97.59	11.775%	$109.0812	$109.08	$109.10	$109.10
Purchase #6	$92.26	8.725%	$100.3097	$100.31	$100.30	$100.30
Purchase #7	$80.44	5.120%	$84.5585	$84.56	$84.55	$84.60
7 purchase totals =	$824.29		$892.9050	$892.90	$892.85	$893.00