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 $68.88   10.605%   $76.1847   $76.18   $76.20   $76.20  
  Purchase #2 $200.27   10.191%   $220.6795   $220.68   $220.70   $220.70  
  Purchase #3 $99.28   12.241%   $111.4329   $111.43   $111.45   $111.40  
  Purchase #4 $84.88   9.311%   $92.7832   $92.78   $92.80   $92.80  
  Purchase #5 $17.27   7.628%   $18.5874   $18.59   $18.60   $18.60  
  Purchase #6 $32.66   4.547%   $34.1451   $34.15   $34.15   $34.10  
  Purchase #7 $72.41   3.227%   $74.7467   $74.75   $74.75   $74.70  
  7 purchase totals = $575.65       $628.5595   $628.56   $628.65   $628.50