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	$212.90	10.300%	$234.8287	$234.83	$234.85	$234.80
Purchase #2	$165.38	8.599%	$179.601	$179.60	$179.60	$179.60
Purchase #3	$161.48	6.664%	$172.241	$172.24	$172.25	$172.20
Purchase #4	$133.35	11.213%	$148.3025	$148.30	$148.30	$148.30
Purchase #5	$17.57	11.748%	$19.6341	$19.63	$19.65	$19.60
Purchase #6	$31.48	9.577%	$34.4948	$34.49	$34.50	$34.50
Purchase #7	$162.76	6.198%	$172.8479	$172.85	$172.85	$172.80
7 purchase totals =	$884.92		$961.9500	$961.94	$962.00	$961.80