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 $143.88   5.667%   $152.0337   $152.03   $152.05   $152.00  
  Purchase #2 $94.39   5.494%   $99.5758   $99.58   $99.60   $99.60  
  Purchase #3 $80.49   5.546%   $84.954   $84.95   $84.95   $85.00  
  Purchase #4 $29.54   12.485%   $33.2281   $33.23   $33.25   $33.20  
  Purchase #5 $196.91   3.678%   $204.1523   $204.15   $204.15   $204.20  
  Purchase #6 $188.29   8.755%   $204.7748   $204.77   $204.75   $204.80  
  Purchase #7 $235.69   4.382%   $246.0179   $246.02   $246.00   $246.00  
  7 purchase totals = $969.19       $1,024.7366   $1,024.73   $1,024.75   $1,024.80