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 $24.63   5.446%   $25.9713   $25.97   $25.95   $26.00  
  Purchase #2 $41.71   12.104%   $46.7586   $46.76   $46.75   $46.80  
  Purchase #3 $177.96   5.578%   $187.8866   $187.89   $187.90   $187.90  
  Purchase #4 $152.92   9.703%   $167.7578   $167.76   $167.75   $167.80  
  Purchase #5 $200.32   8.183%   $216.7122   $216.71   $216.70   $216.70  
  Purchase #6 $247.83   9.479%   $271.3218   $271.32   $271.30   $271.30  
  Purchase #7 $82.93   13.172%   $93.8535   $93.85   $93.85   $93.90  
  7 purchase totals = $928.30       $1,010.2618   $1,010.26   $1,010.20   $1,010.40