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 $51.37   9.352%   $56.1741   $56.17   $56.15   $56.20  
  Purchase #2 $239.94   3.358%   $247.9972   $248.00   $248.00   $248.00  
  Purchase #3 $81.26   7.309%   $87.1993   $87.20   $87.20   $87.20  
  Purchase #4 $65.96   5.391%   $69.5159   $69.52   $69.50   $69.50  
  Purchase #5 $192.76   6.706%   $205.6865   $205.69   $205.70   $205.70  
  Purchase #6 $150.59   4.791%   $157.8048   $157.80   $157.80   $157.80  
  Purchase #7 $179.80   11.545%   $200.5579   $200.56   $200.55   $200.60  
  7 purchase totals = $961.68       $1,024.9357   $1,024.94   $1,024.90   $1,025.00