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	$103.26	8.465%	$112.001	$112.00	$112.00	$112.00
Purchase #2	$125.54	4.420%	$131.0889	$131.09	$131.10	$131.10
Purchase #3	$90.98	8.788%	$98.9753	$98.98	$99.00	$99.00
Purchase #4	$124.60	3.236%	$128.6321	$128.63	$128.65	$128.60
Purchase #5	$141.85	11.787%	$158.5699	$158.57	$158.55	$158.60
Purchase #6	$155.45	10.315%	$171.4847	$171.48	$171.50	$171.50
Purchase #7	$142.78	12.590%	$160.756	$160.76	$160.75	$160.80
7 purchase totals =	$884.46		$961.5079	$961.51	$961.55	$961.60