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	$30.89	5.230%	$32.5055	$32.51	$32.50	$32.50
Purchase #2	$136.82	11.738%	$152.8799	$152.88	$152.90	$152.90
Purchase #3	$78.31	5.847%	$82.8888	$82.89	$82.90	$82.90
Purchase #4	$242.39	13.558%	$275.2532	$275.25	$275.25	$275.30
Purchase #5	$61.96	9.627%	$67.9249	$67.92	$67.90	$67.90
Purchase #6	$132.98	7.455%	$142.8937	$142.89	$142.90	$142.90
Purchase #7	$171.48	11.166%	$190.6275	$190.63	$190.65	$190.60
7 purchase totals =	$854.83		$944.9735	$944.97	$945.00	$945.00