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 $57.87   7.525%   $62.2247   $62.22   $62.20   $62.20  
  Purchase #2 $120.42   3.820%   $125.02   $125.02   $125.00   $125.00  
  Purchase #3 $206.65   7.429%   $222.002   $222.00   $222.00   $222.00  
  Purchase #4 $133.41   3.790%   $138.4662   $138.47   $138.45   $138.50  
  Purchase #5 $26.41   13.312%   $29.9257   $29.93   $29.95   $29.90  
  Purchase #6 $130.99   4.858%   $137.3535   $137.35   $137.35   $137.40  
  Purchase #7 $14.50   4.787%   $15.1941   $15.19   $15.20   $15.20  
  7 purchase totals = $690.25       $730.1862   $730.18   $730.15   $730.20