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 $112.63   11.601%   $125.6962   $125.70   $125.70   $125.70  
  Purchase #2 $49.53   6.867%   $52.9312   $52.93   $52.95   $52.90  
  Purchase #3 $126.65   8.110%   $136.9213   $136.92   $136.90   $136.90  
  Purchase #4 $181.33   3.376%   $187.4517   $187.45   $187.45   $187.50  
  Purchase #5 $180.67   12.281%   $202.8581   $202.86   $202.85   $202.90  
  Purchase #6 $14.93   9.189%   $16.3019   $16.30   $16.30   $16.30  
  Purchase #7 $97.32   6.701%   $103.8414   $103.84   $103.85   $103.80  
  7 purchase totals = $763.06       $826.0018   $826.00   $826.00   $826.00