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	$128.78	10.173%	$141.8808	$141.88	$141.90	$141.90
Purchase #2	$186.48	7.150%	$199.8133	$199.81	$199.80	$199.80
Purchase #3	$223.99	3.508%	$231.8476	$231.85	$231.85	$231.80
Purchase #4	$155.52	5.855%	$164.6257	$164.63	$164.65	$164.60
Purchase #5	$95.94	3.767%	$99.5541	$99.55	$99.55	$99.60
Purchase #6	$122.66	3.812%	$127.3358	$127.34	$127.35	$127.30
Purchase #7	$134.26	9.856%	$147.4927	$147.49	$147.50	$147.50
7 purchase totals =	$1,047.63		$1,112.5500	$1,112.55	$1,112.60	$1,112.50