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 $188.33   3.395%   $194.7238   $194.72   $194.70   $194.70  
  Purchase #2 $216.51   4.509%   $226.2724   $226.27   $226.25   $226.30  
  Purchase #3 $237.79   7.756%   $256.233   $256.23   $256.25   $256.20  
  Purchase #4 $145.80   11.380%   $162.392   $162.39   $162.40   $162.40  
  Purchase #5 $159.28   7.414%   $171.089   $171.09   $171.10   $171.10  
  Purchase #6 $168.75   4.713%   $176.7032   $176.70   $176.70   $176.70  
  Purchase #7 $201.97   12.624%   $227.4667   $227.47   $227.45   $227.50  
  7 purchase totals = $1,318.43       $1,414.8801   $1,414.87   $1,414.85   $1,414.90