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	$111.34	5.558%	$117.5283	$117.53	$117.55	$117.50
Purchase #2	$176.53	4.522%	$184.5127	$184.51	$184.50	$184.50
Purchase #3	$74.31	9.568%	$81.42	$81.42	$81.40	$81.40
Purchase #4	$68.67	5.238%	$72.2669	$72.27	$72.25	$72.30
Purchase #5	$238.29	4.691%	$249.4682	$249.47	$249.45	$249.50
Purchase #6	$212.36	9.188%	$231.8716	$231.87	$231.85	$231.90
Purchase #7	$147.48	6.434%	$156.9689	$156.97	$156.95	$157.00
7 purchase totals =	$1,028.98		$1,094.0366	$1,094.04	$1,093.95	$1,094.10