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 $58.81   6.522%   $62.6456   $62.65   $62.65   $62.60  
  Purchase #2 $107.59   10.724%   $119.128   $119.13   $119.15   $119.10  
  Purchase #3 $180.97   13.597%   $205.5765   $205.58   $205.60   $205.60  
  Purchase #4 $207.26   12.354%   $232.8649   $232.86   $232.85   $232.90  
  Purchase #5 $87.57   6.833%   $93.5537   $93.55   $93.55   $93.60  
  Purchase #6 $124.93   3.294%   $129.0452   $129.05   $129.05   $129.00  
  Purchase #7 $46.30   12.767%   $52.2111   $52.21   $52.20   $52.20  
  7 purchase totals = $813.43       $895.0250   $895.03   $895.05   $895.00