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 $83.53   13.293%   $94.6336   $94.63   $94.65   $94.60  
  Purchase #2 $208.58   11.587%   $232.7482   $232.75   $232.75   $232.70  
  Purchase #3 $78.98   9.461%   $86.4523   $86.45   $86.45   $86.50  
  Purchase #4 $104.42   8.299%   $113.0858   $113.09   $113.10   $113.10  
  Purchase #5 $64.49   13.497%   $73.1942   $73.19   $73.20   $73.20  
  Purchase #6 $226.82   13.279%   $256.9394   $256.94   $256.95   $256.90  
  Purchase #7 $163.53   10.759%   $181.1242   $181.12   $181.10   $181.10  
  7 purchase totals = $930.35       $1,038.1777   $1,038.17   $1,038.20   $1,038.10