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 $58.47   5.710%   $61.8086   $61.81   $61.80   $61.80  
  Purchase #2 $241.37   7.431%   $259.3062   $259.31   $259.30   $259.30  
  Purchase #3 $60.29   8.160%   $65.2097   $65.21   $65.20   $65.20  
  Purchase #4 $130.95   12.104%   $146.8002   $146.80   $146.80   $146.80  
  Purchase #5 $205.75   8.776%   $223.8066   $223.81   $223.80   $223.80  
  Purchase #6 $222.81   7.606%   $239.7569   $239.76   $239.75   $239.80  
  Purchase #7 $176.31   11.356%   $196.3318   $196.33   $196.35   $196.30  
  7 purchase totals = $1,095.95       $1,193.0200   $1,193.03   $1,193.00   $1,193.00