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 $195.65   3.828%   $203.1395   $203.14   $203.15   $203.10  
  Purchase #2 $241.97   8.452%   $262.4213   $262.42   $262.40   $262.40  
  Purchase #3 $8.54   9.425%   $9.3449   $9.34   $9.35   $9.30  
  Purchase #4 $227.90   11.562%   $254.2498   $254.25   $254.25   $254.20  
  Purchase #5 $61.91   10.861%   $68.634   $68.63   $68.65   $68.60  
  Purchase #6 $144.72   6.215%   $153.7143   $153.71   $153.70   $153.70  
  Purchase #7 $41.40   6.626%   $44.1432   $44.14   $44.15   $44.10  
  7 purchase totals = $922.09       $995.6470   $995.63   $995.65   $995.40