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	$185.60	10.826%	$205.6931	$205.69	$205.70	$205.70
Purchase #2	$84.90	10.507%	$93.8204	$93.82	$93.80	$93.80
Purchase #3	$50.28	13.824%	$57.2307	$57.23	$57.25	$57.20
Purchase #4	$43.47	4.515%	$45.4327	$45.43	$45.45	$45.40
Purchase #5	$213.47	13.391%	$242.0558	$242.06	$242.05	$242.10
Purchase #6	$40.75	6.668%	$43.4672	$43.47	$43.45	$43.50
Purchase #7	$121.29	11.171%	$134.8393	$134.84	$134.85	$134.80
7 purchase totals =	$739.76		$822.5392	$822.54	$822.55	$822.50