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	$86.25	6.259%	$91.6484	$91.65	$91.65	$91.60
Purchase #2	$86.41	13.163%	$97.7841	$97.78	$97.80	$97.80
Purchase #3	$60.64	3.198%	$62.5793	$62.58	$62.60	$62.60
Purchase #4	$93.42	7.679%	$100.5937	$100.59	$100.60	$100.60
Purchase #5	$228.30	13.204%	$258.4447	$258.44	$258.45	$258.40
Purchase #6	$35.93	11.606%	$40.1	$40.10	$40.10	$40.10
Purchase #7	$90.32	10.559%	$99.8569	$99.86	$99.85	$99.90
7 purchase totals =	$681.27		$751.0071	$751.00	$751.05	$751.00