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 $82.41   3.791%   $85.5342   $85.53   $85.55   $85.50  
  Purchase #2 $196.93   4.494%   $205.78   $205.78   $205.80   $205.80  
  Purchase #3 $58.46   7.133%   $62.63   $62.63   $62.65   $62.60  
  Purchase #4 $161.91   9.369%   $177.0793   $177.08   $177.10   $177.10  
  Purchase #5 $138.89   6.227%   $147.5387   $147.54   $147.55   $147.50  
  Purchase #6 $21.48   10.386%   $23.7109   $23.71   $23.70   $23.70  
  Purchase #7 $154.41   6.456%   $164.3787   $164.38   $164.40   $164.40  
  7 purchase totals = $814.49       $866.6518   $866.65   $866.75   $866.60