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 $239.86   8.526%   $260.3105   $260.31   $260.30   $260.30  
  Purchase #2 $67.95   3.588%   $70.388   $70.39   $70.40   $70.40  
  Purchase #3 $110.50   13.112%   $124.9888   $124.99   $125.00   $125.00  
  Purchase #4 $93.40   5.111%   $98.1737   $98.17   $98.15   $98.20  
  Purchase #5 $201.43   12.148%   $225.8997   $225.90   $225.90   $225.90  
  Purchase #6 $176.98   4.201%   $184.4149   $184.41   $184.40   $184.40  
  Purchase #7 $116.67   12.738%   $131.5314   $131.53   $131.55   $131.50  
  7 purchase totals = $1,006.79       $1,095.7070   $1,095.70   $1,095.70   $1,095.70