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 $22.57   5.553%   $23.8233   $23.82   $23.80   $23.80  
  Purchase #2 $119.27   6.651%   $127.2026   $127.20   $127.20   $127.20  
  Purchase #3 $42.86   6.386%   $45.597   $45.60   $45.60   $45.60  
  Purchase #4 $122.34   6.616%   $130.434   $130.43   $130.45   $130.40  
  Purchase #5 $62.90   4.542%   $65.7569   $65.76   $65.75   $65.80  
  Purchase #6 $86.77   7.453%   $93.237   $93.24   $93.25   $93.20  
  Purchase #7 $218.37   10.460%   $241.2115   $241.21   $241.20   $241.20  
  7 purchase totals = $675.08       $727.2623   $727.26   $727.25   $727.20