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 $114.49   3.310%   $118.2796   $118.28   $118.30   $118.30  
  Purchase #2 $113.30   7.590%   $121.8995   $121.90   $121.90   $121.90  
  Purchase #3 $197.87   5.589%   $208.929   $208.93   $208.95   $208.90  
  Purchase #4 $120.91   11.119%   $134.354   $134.35   $134.35   $134.40  
  Purchase #5 $200.28   3.197%   $206.683   $206.68   $206.70   $206.70  
  Purchase #6 $145.68   5.591%   $153.825   $153.83   $153.85   $153.80  
  Purchase #7 $141.66   7.715%   $152.5891   $152.59   $152.60   $152.60  
  7 purchase totals = $1,034.19       $1,096.5592   $1,096.56   $1,096.65   $1,096.60