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	$214.47	4.822%	$224.8117	$224.81	$224.80	$224.80
Purchase #2	$185.58	3.128%	$191.3849	$191.38	$191.40	$191.40
Purchase #3	$171.89	8.341%	$186.2273	$186.23	$186.25	$186.20
Purchase #4	$249.50	6.440%	$265.5678	$265.57	$265.55	$265.60
Purchase #5	$131.37	8.437%	$142.4537	$142.45	$142.45	$142.50
Purchase #6	$40.46	4.587%	$42.3159	$42.32	$42.30	$42.30
Purchase #7	$72.96	11.681%	$81.4825	$81.48	$81.50	$81.50
7 purchase totals =	$1,066.23		$1,134.2438	$1,134.24	$1,134.25	$1,134.30