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 $58.39   11.418%   $65.057   $65.06   $65.05   $65.10  
  Purchase #2 $149.40   4.788%   $156.5533   $156.55   $156.55   $156.60  
  Purchase #3 $62.41   5.679%   $65.9543   $65.95   $65.95   $66.00  
  Purchase #4 $45.68   7.745%   $49.2179   $49.22   $49.20   $49.20  
  Purchase #5 $250.68   6.646%   $267.3402   $267.34   $267.35   $267.30  
  Purchase #6 $59.52   9.811%   $65.3595   $65.36   $65.35   $65.40  
  Purchase #7 $107.84   4.795%   $113.0109   $113.01   $113.00   $113.00  
  7 purchase totals = $733.92       $782.4931   $782.49   $782.45   $782.60