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 $47.79   13.115%   $54.0577   $54.06   $54.05   $54.10  
  Purchase #2 $176.40   10.603%   $195.1037   $195.10   $195.10   $195.10  
  Purchase #3 $106.66   6.635%   $113.7369   $113.74   $113.75   $113.70  
  Purchase #4 $112.68   13.147%   $127.494   $127.49   $127.50   $127.50  
  Purchase #5 $87.38   3.193%   $90.17   $90.17   $90.15   $90.20  
  Purchase #6 $129.57   10.774%   $143.5299   $143.53   $143.55   $143.50  
  Purchase #7 $46.72   4.437%   $48.793   $48.79   $48.80   $48.80  
  7 purchase totals = $707.20       $772.8852   $772.88   $772.90   $772.90