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	$86.65	6.821%	$92.5604	$92.56	$92.55	$92.60
Purchase #2	$119.92	9.772%	$131.6386	$131.64	$131.65	$131.60
Purchase #3	$29.91	4.576%	$31.2787	$31.28	$31.30	$31.30
Purchase #4	$223.52	6.255%	$237.5012	$237.50	$237.50	$237.50
Purchase #5	$230.59	12.334%	$259.031	$259.03	$259.05	$259.00
Purchase #6	$40.65	7.281%	$43.6097	$43.61	$43.60	$43.60
Purchase #7	$54.56	11.829%	$61.0139	$61.01	$61.00	$61.00
7 purchase totals =	$785.80		$856.6335	$856.63	$856.65	$856.60