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 $58.95   5.793%   $62.365   $62.37   $62.35   $62.40  
  Purchase #2 $64.65   3.397%   $66.8462   $66.85   $66.85   $66.80  
  Purchase #3 $43.72   4.457%   $45.6686   $45.67   $45.65   $45.70  
  Purchase #4 $157.79   3.621%   $163.5036   $163.50   $163.50   $163.50  
  Purchase #5 $225.57   5.768%   $238.5809   $238.58   $238.60   $238.60  
  Purchase #6 $208.46   6.356%   $221.7097   $221.71   $221.70   $221.70  
  Purchase #7 $92.96   6.383%   $98.8936   $98.89   $98.90   $98.90  
  7 purchase totals = $852.10       $897.5676   $897.57   $897.55   $897.60