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	$96.33	8.138%	$104.1693	$104.17	$104.15	$104.20
Purchase #2	$80.36	3.590%	$83.2449	$83.24	$83.25	$83.20
Purchase #3	$65.51	10.436%	$72.3466	$72.35	$72.35	$72.30
Purchase #4	$246.71	9.291%	$269.6318	$269.63	$269.65	$269.60
Purchase #5	$144.47	6.483%	$153.836	$153.84	$153.85	$153.80
Purchase #6	$40.95	5.775%	$43.3149	$43.31	$43.30	$43.30
Purchase #7	$162.39	10.870%	$180.0418	$180.04	$180.05	$180.00
7 purchase totals =	$836.72		$906.5853	$906.58	$906.60	$906.40