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	$164.56	9.558%	$180.2886	$180.29	$180.30	$180.30
Purchase #2	$195.67	8.632%	$212.5602	$212.56	$212.55	$212.60
Purchase #3	$109.61	10.259%	$120.8549	$120.85	$120.85	$120.90
Purchase #4	$63.61	5.153%	$66.8878	$66.89	$66.90	$66.90
Purchase #5	$134.79	7.274%	$144.5946	$144.59	$144.60	$144.60
Purchase #6	$80.67	13.834%	$91.8299	$91.83	$91.85	$91.80
Purchase #7	$249.37	13.867%	$283.9501	$283.95	$283.95	$284.00
7 purchase totals =	$998.28		$1,100.9661	$1,100.96	$1,101.00	$1,101.10