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	$121.31	3.765%	$125.8773	$125.88	$125.90	$125.90
Purchase #2	$61.29	4.219%	$63.8758	$63.88	$63.90	$63.90
Purchase #3	$169.88	12.348%	$190.8568	$190.86	$190.85	$190.90
Purchase #4	$168.36	7.775%	$181.45	$181.45	$181.45	$181.50
Purchase #5	$127.77	13.198%	$144.6331	$144.63	$144.65	$144.60
Purchase #6	$187.48	6.831%	$200.2868	$200.29	$200.30	$200.30
Purchase #7	$142.47	4.194%	$148.4452	$148.45	$148.45	$148.40
7 purchase totals =	$978.56		$1,055.4250	$1,055.44	$1,055.50	$1,055.50