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	$141.68	7.703%	$152.5936	$152.59	$152.60	$152.60
Purchase #2	$106.81	8.447%	$115.8322	$115.83	$115.85	$115.80
Purchase #3	$94.89	8.798%	$103.2384	$103.24	$103.25	$103.20
Purchase #4	$139.39	5.814%	$147.4941	$147.49	$147.50	$147.50
Purchase #5	$109.30	10.316%	$120.5754	$120.58	$120.60	$120.60
Purchase #6	$130.34	5.505%	$137.5152	$137.52	$137.50	$137.50
Purchase #7	$178.37	5.302%	$187.8272	$187.83	$187.85	$187.80
7 purchase totals =	$900.78		$965.0761	$965.08	$965.15	$965.00