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 $92.35   10.734%   $102.2628   $102.26   $102.25   $102.30  
  Purchase #2 $101.78   8.678%   $110.6125   $110.61   $110.60   $110.60  
  Purchase #3 $181.88   3.854%   $188.8897   $188.89   $188.90   $188.90  
  Purchase #4 $181.40   11.184%   $201.6878   $201.69   $201.70   $201.70  
  Purchase #5 $237.50   5.826%   $251.3368   $251.34   $251.35   $251.30  
  Purchase #6 $95.86   8.837%   $104.3311   $104.33   $104.35   $104.30  
  Purchase #7 $152.61   9.235%   $166.7035   $166.70   $166.70   $166.70  
  7 purchase totals = $1,043.38       $1,125.8242   $1,125.82   $1,125.85   $1,125.80