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 $89.92   6.110%   $95.4141   $95.41   $95.40   $95.40  
  Purchase #2 $206.51   7.850%   $222.721   $222.72   $222.70   $222.70  
  Purchase #3 $54.41   7.600%   $58.5452   $58.55   $58.55   $58.50  
  Purchase #4 $164.53   12.185%   $184.578   $184.58   $184.60   $184.60  
  Purchase #5 $239.92   8.713%   $260.8242   $260.82   $260.80   $260.80  
  Purchase #6 $220.59   7.304%   $236.7019   $236.70   $236.70   $236.70  
  Purchase #7 $27.44   8.521%   $29.7782   $29.78   $29.80   $29.80  
  7 purchase totals = $1,003.32       $1,088.5626   $1,088.56   $1,088.55   $1,088.50