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 $75.86   10.116%   $83.534   $83.53   $83.55   $83.50  
  Purchase #2 $174.43   7.534%   $187.5716   $187.57   $187.55   $187.60  
  Purchase #3 $201.41   10.808%   $223.1784   $223.18   $223.20   $223.20  
  Purchase #4 $229.80   7.361%   $246.7156   $246.72   $246.70   $246.70  
  Purchase #5 $122.50   12.369%   $137.652   $137.65   $137.65   $137.70  
  Purchase #6 $112.79   8.797%   $122.7121   $122.71   $122.70   $122.70  
  Purchase #7 $57.29   6.435%   $60.9766   $60.98   $61.00   $61.00  
  7 purchase totals = $974.08       $1,062.3403   $1,062.34   $1,062.35   $1,062.40