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 $220.71   7.639%   $237.57   $237.57   $237.55   $237.60  
  Purchase #2 $80.83   8.594%   $87.7765   $87.78   $87.80   $87.80  
  Purchase #3 $15.80   10.212%   $17.4135   $17.41   $17.40   $17.40  
  Purchase #4 $46.32   9.232%   $50.5963   $50.60   $50.60   $50.60  
  Purchase #5 $116.92   12.846%   $131.9395   $131.94   $131.95   $131.90  
  Purchase #6 $204.32   10.673%   $226.1271   $226.13   $226.15   $226.10  
  Purchase #7 $239.26   9.801%   $262.7099   $262.71   $262.70   $262.70  
  7 purchase totals = $924.16       $1,014.1328   $1,014.14   $1,014.15   $1,014.10