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 $204.84   8.504%   $222.2596   $222.26   $222.25   $222.30  
  Purchase #2 $230.31   6.652%   $245.6302   $245.63   $245.65   $245.60  
  Purchase #3 $61.87   9.774%   $67.9172   $67.92   $67.90   $67.90  
  Purchase #4 $106.51   8.817%   $115.901   $115.90   $115.90   $115.90  
  Purchase #5 $214.98   11.433%   $239.5587   $239.56   $239.55   $239.60  
  Purchase #6 $51.85   7.807%   $55.8979   $55.90   $55.90   $55.90  
  Purchase #7 $193.38   7.342%   $207.578   $207.58   $207.60   $207.60  
  7 purchase totals = $1,063.74       $1,154.7426   $1,154.75   $1,154.75   $1,154.80