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 $60.31   3.378%   $62.3473   $62.35   $62.35   $62.30  
  Purchase #2 $173.61   11.393%   $193.3894   $193.39   $193.40   $193.40  
  Purchase #3 $54.93   5.730%   $58.0775   $58.08   $58.10   $58.10  
  Purchase #4 $51.85   5.474%   $54.6883   $54.69   $54.70   $54.70  
  Purchase #5 $223.92   5.135%   $235.4183   $235.42   $235.40   $235.40  
  Purchase #6 $74.34   12.686%   $83.7708   $83.77   $83.75   $83.80  
  Purchase #7 $114.42   7.214%   $122.6743   $122.67   $122.65   $122.70  
  7 purchase totals = $753.38       $810.3659   $810.37   $810.35   $810.40