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 $84.47   12.568%   $95.0862   $95.09   $95.10   $95.10  
  Purchase #2 $234.40   7.443%   $251.8464   $251.85   $251.85   $251.80  
  Purchase #3 $57.98   10.345%   $63.978   $63.98   $64.00   $64.00  
  Purchase #4 $208.76   6.790%   $222.9348   $222.93   $222.95   $222.90  
  Purchase #5 $188.82   5.493%   $199.1919   $199.19   $199.20   $199.20  
  Purchase #6 $159.68   4.405%   $166.7139   $166.71   $166.70   $166.70  
  Purchase #7 $106.87   5.614%   $112.8697   $112.87   $112.85   $112.90  
  7 purchase totals = $1,040.98       $1,112.6209   $1,112.62   $1,112.65   $1,112.60