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 $213.76   10.279%   $235.7324   $235.73   $235.75   $235.70  
  Purchase #2 $189.66   3.671%   $196.6224   $196.62   $196.60   $196.60  
  Purchase #3 $178.98   12.707%   $201.723   $201.72   $201.70   $201.70  
  Purchase #4 $82.59   12.744%   $93.1153   $93.12   $93.10   $93.10  
  Purchase #5 $216.27   13.668%   $245.8298   $245.83   $245.85   $245.80  
  Purchase #6 $62.87   6.122%   $66.7189   $66.72   $66.70   $66.70  
  Purchase #7 $211.70   5.610%   $223.5764   $223.58   $223.60   $223.60  
  7 purchase totals = $1,155.83       $1,263.3182   $1,263.32   $1,263.30   $1,263.20