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 $76.83   7.817%   $82.8358   $82.84   $82.85   $82.80  
  Purchase #2 $151.32   8.507%   $164.1928   $164.19   $164.20   $164.20  
  Purchase #3 $80.98   7.728%   $87.2381   $87.24   $87.25   $87.20  
  Purchase #4 $245.92   8.486%   $266.7888   $266.79   $266.80   $266.80  
  Purchase #5 $82.69   13.624%   $93.9557   $93.96   $93.95   $94.00  
  Purchase #6 $197.31   10.313%   $217.6586   $217.66   $217.65   $217.70  
  Purchase #7 $136.53   7.275%   $146.4626   $146.46   $146.45   $146.50  
  7 purchase totals = $971.58       $1,059.1324   $1,059.14   $1,059.15   $1,059.20