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 $58.46   5.136%   $61.4625   $61.46   $61.45   $61.50  
  Purchase #2 $38.54   8.259%   $41.723   $41.72   $41.70   $41.70  
  Purchase #3 $190.98   9.767%   $209.633   $209.63   $209.65   $209.60  
  Purchase #4 $247.33   6.734%   $263.9852   $263.99   $264.00   $264.00  
  Purchase #5 $88.79   10.330%   $97.962   $97.96   $97.95   $98.00  
  Purchase #6 $165.63   5.550%   $174.8225   $174.82   $174.80   $174.80  
  Purchase #7 $141.45   9.456%   $154.8255   $154.83   $154.85   $154.80  
  7 purchase totals = $931.18       $1,004.4137   $1,004.41   $1,004.40   $1,004.40