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 $59.95   5.189%   $63.0608   $63.06   $63.05   $63.10  
  Purchase #2 $216.87   11.399%   $241.591   $241.59   $241.60   $241.60  
  Purchase #3 $67.25   5.133%   $70.7019   $70.70   $70.70   $70.70  
  Purchase #4 $49.68   7.204%   $53.2589   $53.26   $53.25   $53.30  
  Purchase #5 $121.68   11.481%   $135.6501   $135.65   $135.65   $135.70  
  Purchase #6 $168.48   9.729%   $184.8714   $184.87   $184.85   $184.90  
  Purchase #7 $111.81   5.400%   $117.8477   $117.85   $117.85   $117.80  
  7 purchase totals = $795.72       $866.9818   $866.98   $866.95   $867.10