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	$166.48	6.210%	$176.8184	$176.82	$176.80	$176.80
Purchase #2	$35.84	5.561%	$37.8331	$37.83	$37.85	$37.80
Purchase #3	$245.64	3.822%	$255.0284	$255.03	$255.05	$255.00
Purchase #4	$144.99	4.416%	$151.3928	$151.39	$151.40	$151.40
Purchase #5	$178.61	11.761%	$199.6163	$199.62	$199.60	$199.60
Purchase #6	$41.86	3.780%	$43.4423	$43.44	$43.45	$43.40
Purchase #7	$134.57	13.630%	$152.9119	$152.91	$152.90	$152.90
7 purchase totals =	$947.99		$1,017.0432	$1,017.04	$1,017.05	$1,016.90