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 $207.86   12.447%   $233.7323   $233.73   $233.75   $233.70  
  Purchase #2 $63.58   3.340%   $65.7036   $65.70   $65.70   $65.70  
  Purchase #3 $115.73   3.159%   $119.3859   $119.39   $119.40   $119.40  
  Purchase #4 $198.28   13.416%   $224.8812   $224.88   $224.90   $224.90  
  Purchase #5 $221.68   3.102%   $228.5565   $228.56   $228.55   $228.60  
  Purchase #6 $138.96   3.775%   $144.2057   $144.21   $144.20   $144.20  
  Purchase #7 $46.89   7.573%   $50.441   $50.44   $50.45   $50.40  
  7 purchase totals = $992.98       $1,066.9062   $1,066.91   $1,066.95   $1,066.90