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 $217.88   8.294%   $235.951   $235.95   $235.95   $236.00  
  Purchase #2 $61.72   10.773%   $68.3691   $68.37   $68.35   $68.40  
  Purchase #3 $27.42   6.357%   $29.1631   $29.16   $29.15   $29.20  
  Purchase #4 $148.45   8.273%   $160.7313   $160.73   $160.75   $160.70  
  Purchase #5 $223.90   11.359%   $249.3328   $249.33   $249.35   $249.30  
  Purchase #6 $247.71   4.519%   $258.904   $258.90   $258.90   $258.90  
  Purchase #7 $21.46   13.778%   $24.4168   $24.42   $24.40   $24.40  
  7 purchase totals = $948.54       $1,026.8681   $1,026.86   $1,026.85   $1,026.90