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	$39.58	4.328%	$41.293	$41.29	$41.30	$41.30
Purchase #2	$38.25	11.231%	$42.5459	$42.55	$42.55	$42.50
Purchase #3	$227.87	13.762%	$259.2295	$259.23	$259.25	$259.20
Purchase #4	$244.72	5.620%	$258.4733	$258.47	$258.45	$258.50
Purchase #5	$92.88	3.349%	$95.9906	$95.99	$96.00	$96.00
Purchase #6	$194.58	12.277%	$218.4686	$218.47	$218.45	$218.50
Purchase #7	$96.71	13.598%	$109.8606	$109.86	$109.85	$109.90
7 purchase totals =	$934.59		$1,025.8615	$1,025.86	$1,025.85	$1,025.90