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 $59.35   5.721%   $62.7454   $62.75   $62.75   $62.70  
  Purchase #2 $106.77   3.393%   $110.3927   $110.39   $110.40   $110.40  
  Purchase #3 $126.70   5.804%   $134.0537   $134.05   $134.05   $134.10  
  Purchase #4 $207.58   8.635%   $225.5045   $225.50   $225.50   $225.50  
  Purchase #5 $183.96   13.517%   $208.8259   $208.83   $208.85   $208.80  
  Purchase #6 $46.89   7.385%   $50.3528   $50.35   $50.35   $50.40  
  Purchase #7 $94.38   6.421%   $100.4401   $100.44   $100.45   $100.40  
  7 purchase totals = $825.63       $892.3151   $892.31   $892.35   $892.30