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 $58.81   5.780%   $62.2092   $62.21   $62.20   $62.20  
  Purchase #2 $34.56   9.790%   $37.9434   $37.94   $37.95   $37.90  
  Purchase #3 $106.45   13.388%   $120.7015   $120.70   $120.70   $120.70  
  Purchase #4 $186.85   3.777%   $193.9073   $193.91   $193.90   $193.90  
  Purchase #5 $83.32   12.511%   $93.7442   $93.74   $93.75   $93.70  
  Purchase #6 $191.63   4.668%   $200.5753   $200.58   $200.60   $200.60  
  Purchase #7 $48.32   6.490%   $51.456   $51.46   $51.45   $51.50  
  7 purchase totals = $709.94       $760.5369   $760.54   $760.55   $760.50