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	$182.32	8.830%	$198.4189	$198.42	$198.40	$198.40
Purchase #2	$199.38	7.328%	$213.9906	$213.99	$214.00	$214.00
Purchase #3	$68.96	5.244%	$72.5763	$72.58	$72.60	$72.60
Purchase #4	$124.27	12.481%	$139.7801	$139.78	$139.80	$139.80
Purchase #5	$111.38	9.465%	$121.9221	$121.92	$121.90	$121.90
Purchase #6	$103.30	7.708%	$111.2624	$111.26	$111.25	$111.30
Purchase #7	$18.77	11.270%	$20.8854	$20.89	$20.90	$20.90
7 purchase totals =	$808.38		$878.8358	$878.84	$878.85	$878.90