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 $62.64   8.636%   $68.0496   $68.05   $68.05   $68.00  
  Purchase #2 $234.90   7.119%   $251.6225   $251.62   $251.60   $251.60  
  Purchase #3 $120.53   10.425%   $133.0953   $133.10   $133.10   $133.10  
  Purchase #4 $220.69   7.691%   $237.6633   $237.66   $237.65   $237.70  
  Purchase #5 $236.63   12.588%   $266.417   $266.42   $266.40   $266.40  
  Purchase #6 $141.33   10.484%   $156.147   $156.15   $156.15   $156.10  
  Purchase #7 $165.74   11.765%   $185.2393   $185.24   $185.25   $185.20  
  7 purchase totals = $1,182.46       $1,298.2340   $1,298.24   $1,298.20   $1,298.10