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 $56.46   7.503%   $60.6962   $60.70   $60.70   $60.70  
  Purchase #2 $49.95   9.595%   $54.7427   $54.74   $54.75   $54.70  
  Purchase #3 $85.36   7.225%   $91.5273   $91.53   $91.55   $91.50  
  Purchase #4 $191.56   13.744%   $217.888   $217.89   $217.90   $217.90  
  Purchase #5 $240.64   9.786%   $264.189   $264.19   $264.20   $264.20  
  Purchase #6 $207.53   8.170%   $224.4852   $224.49   $224.50   $224.50  
  Purchase #7 $130.52   6.123%   $138.5117   $138.51   $138.50   $138.50  
  7 purchase totals = $962.02       $1,052.0401   $1,052.05   $1,052.10   $1,052.00