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 $60.30   3.871%   $62.6342   $62.63   $62.65   $62.60  
  Purchase #2 $181.92   6.257%   $193.3027   $193.30   $193.30   $193.30  
  Purchase #3 $58.67   5.737%   $62.0359   $62.04   $62.05   $62.00  
  Purchase #4 $128.34   4.206%   $133.738   $133.74   $133.75   $133.70  
  Purchase #5 $44.82   4.687%   $46.9207   $46.92   $46.90   $46.90  
  Purchase #6 $223.88   13.779%   $254.7284   $254.73   $254.75   $254.70  
  Purchase #7 $89.93   10.192%   $99.0957   $99.10   $99.10   $99.10  
  7 purchase totals = $787.86       $852.4556   $852.46   $852.50   $852.30