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	$167.57	10.768%	$185.6139	$185.61	$185.60	$185.60
Purchase #2	$233.34	10.139%	$256.9983	$257.00	$257.00	$257.00
Purchase #3	$56.36	6.325%	$59.9248	$59.92	$59.90	$59.90
Purchase #4	$200.93	6.214%	$213.4158	$213.42	$213.40	$213.40
Purchase #5	$137.82	6.602%	$146.9189	$146.92	$146.90	$146.90
Purchase #6	$121.60	5.482%	$128.2661	$128.27	$128.25	$128.30
Purchase #7	$42.65	6.214%	$45.3003	$45.30	$45.30	$45.30
7 purchase totals =	$960.27		$1,036.4381	$1,036.44	$1,036.35	$1,036.40