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 $59.57   4.312%   $62.1387   $62.14   $62.15   $62.10  
  Purchase #2 $198.42   13.507%   $225.2206   $225.22   $225.20   $225.20  
  Purchase #3 $128.26   9.259%   $140.1356   $140.14   $140.15   $140.10  
  Purchase #4 $45.31   3.587%   $46.9353   $46.94   $46.95   $46.90  
  Purchase #5 $222.81   10.317%   $245.7973   $245.80   $245.80   $245.80  
  Purchase #6 $165.93   12.626%   $186.8803   $186.88   $186.90   $186.90  
  Purchase #7 $57.75   4.564%   $60.3857   $60.39   $60.40   $60.40  
  7 purchase totals = $878.05       $967.4935   $967.51   $967.55   $967.40