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 $64.58   3.446%   $66.8054   $66.81   $66.80   $66.80  
  Purchase #2 $155.65   9.181%   $169.9402   $169.94   $169.95   $169.90  
  Purchase #3 $197.86   9.372%   $216.4034   $216.40   $216.40   $216.40  
  Purchase #4 $211.66   9.386%   $231.5264   $231.53   $231.55   $231.50  
  Purchase #5 $218.81   10.452%   $241.68   $241.68   $241.70   $241.70  
  Purchase #6 $214.28   3.842%   $222.5126   $222.51   $222.50   $222.50  
  Purchase #7 $59.47   7.536%   $63.9517   $63.95   $63.95   $64.00  
  7 purchase totals = $1,122.31       $1,212.8197   $1,212.82   $1,212.85   $1,212.80