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	$199.32	12.788%	$224.809	$224.81	$224.80	$224.80
Purchase #2	$86.38	12.715%	$97.3632	$97.36	$97.35	$97.40
Purchase #3	$157.70	6.455%	$167.8795	$167.88	$167.90	$167.90
Purchase #4	$137.59	7.150%	$147.4277	$147.43	$147.45	$147.40
Purchase #5	$182.59	6.486%	$194.4328	$194.43	$194.45	$194.40
Purchase #6	$141.50	6.291%	$150.4018	$150.40	$150.40	$150.40
Purchase #7	$188.82	5.118%	$198.4838	$198.48	$198.50	$198.50
7 purchase totals =	$1,093.90		$1,180.7978	$1,180.79	$1,180.85	$1,180.80