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 $59.43   9.342%   $64.982   $64.98   $65.00   $65.00  
  Purchase #2 $113.61   3.346%   $117.4114   $117.41   $117.40   $117.40  
  Purchase #3 $54.71   12.160%   $61.3627   $61.36   $61.35   $61.40  
  Purchase #4 $60.79   3.247%   $62.7639   $62.76   $62.75   $62.80  
  Purchase #5 $88.48   5.414%   $93.2703   $93.27   $93.25   $93.30  
  Purchase #6 $177.94   13.447%   $201.8676   $201.87   $201.85   $201.90  
  Purchase #7 $197.50   7.228%   $211.7753   $211.78   $211.80   $211.80  
  7 purchase totals = $752.46       $813.4332   $813.43   $813.40   $813.60