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 $46.25   4.362%   $48.2674   $48.27   $48.25   $48.30  
  Purchase #2 $239.84   4.569%   $250.7983   $250.80   $250.80   $250.80  
  Purchase #3 $195.49   10.527%   $216.0692   $216.07   $216.05   $216.10  
  Purchase #4 $197.53   8.869%   $215.0489   $215.05   $215.05   $215.00  
  Purchase #5 $133.98   7.191%   $143.6145   $143.61   $143.60   $143.60  
  Purchase #6 $27.65   11.761%   $30.9019   $30.90   $30.90   $30.90  
  Purchase #7 $154.53   7.469%   $166.0718   $166.07   $166.05   $166.10  
  7 purchase totals = $995.27       $1,070.7720   $1,070.77   $1,070.70   $1,070.80