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 $87.49   9.553%   $95.8479   $95.85   $95.85   $95.80  
  Purchase #2 $43.29   7.803%   $46.6679   $46.67   $46.65   $46.70  
  Purchase #3 $222.60   10.448%   $245.8572   $245.86   $245.85   $245.90  
  Purchase #4 $132.30   8.744%   $143.8683   $143.87   $143.85   $143.90  
  Purchase #5 $150.67   5.342%   $158.7188   $158.72   $158.70   $158.70  
  Purchase #6 $69.78   8.125%   $75.4496   $75.45   $75.45   $75.40  
  Purchase #7 $179.71   3.735%   $186.4222   $186.42   $186.40   $186.40  
  7 purchase totals = $885.84       $952.8319   $952.84   $952.75   $952.80