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	$76.25	13.271%	$86.3691	$86.37	$86.35	$86.40
Purchase #2	$99.30	4.507%	$103.7755	$103.78	$103.80	$103.80
Purchase #3	$237.57	8.296%	$257.2788	$257.28	$257.30	$257.30
Purchase #4	$112.83	13.804%	$128.4051	$128.41	$128.40	$128.40
Purchase #5	$235.63	9.831%	$258.7948	$258.79	$258.80	$258.80
Purchase #6	$139.82	7.482%	$150.2813	$150.28	$150.30	$150.30
Purchase #7	$16.53	10.602%	$18.2825	$18.28	$18.30	$18.30
7 purchase totals =	$917.93		$1,003.1871	$1,003.19	$1,003.25	$1,003.30