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 $61.73   5.313%   $65.0097   $65.01   $65.00   $65.00  
  Purchase #2 $23.97   7.125%   $25.6779   $25.68   $25.70   $25.70  
  Purchase #3 $244.76   4.330%   $255.3581   $255.36   $255.35   $255.40  
  Purchase #4 $114.62   13.689%   $130.3103   $130.31   $130.30   $130.30  
  Purchase #5 $136.58   4.486%   $142.707   $142.71   $142.70   $142.70  
  Purchase #6 $221.96   4.602%   $232.1746   $232.17   $232.15   $232.20  
  Purchase #7 $160.58   12.596%   $180.8067   $180.81   $180.80   $180.80  
  7 purchase totals = $964.20       $1,032.0443   $1,032.05   $1,032.00   $1,032.10