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 $49.43   5.258%   $52.029   $52.03   $52.05   $52.00  
  Purchase #2 $250.99   3.842%   $260.633   $260.63   $260.65   $260.60  
  Purchase #3 $56.27   6.396%   $59.869   $59.87   $59.85   $59.90  
  Purchase #4 $94.95   6.692%   $101.3041   $101.30   $101.30   $101.30  
  Purchase #5 $152.93   4.717%   $160.1437   $160.14   $160.15   $160.10  
  Purchase #6 $87.29   13.530%   $99.1003   $99.10   $99.10   $99.10  
  Purchase #7 $31.63   11.390%   $35.2327   $35.23   $35.25   $35.20  
  7 purchase totals = $723.49       $768.3118   $768.30   $768.35   $768.20