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	$81.84	12.813%	$92.3262	$92.33	$92.35	$92.30
Purchase #2	$43.60	12.255%	$48.9432	$48.94	$48.95	$48.90
Purchase #3	$31.80	6.588%	$33.895	$33.90	$33.90	$33.90
Purchase #4	$6.44	9.835%	$7.0734	$7.07	$7.05	$7.10
Purchase #5	$40.47	13.512%	$45.9383	$45.94	$45.95	$45.90
Purchase #6	$175.43	12.278%	$196.9693	$196.97	$196.95	$197.00
Purchase #7	$138.93	4.270%	$144.8623	$144.86	$144.85	$144.90
7 purchase totals =	$518.51		$570.0077	$570.01	$570.00	$570.00