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 $45.57   5.467%   $48.0613   $48.06   $48.05   $48.10  
  Purchase #2 $224.87   11.584%   $250.9189   $250.92   $250.90   $250.90  
  Purchase #3 $209.54   4.749%   $219.4911   $219.49   $219.50   $219.50  
  Purchase #4 $124.61   8.147%   $134.762   $134.76   $134.75   $134.80  
  Purchase #5 $191.79   5.212%   $201.7861   $201.79   $201.80   $201.80  
  Purchase #6 $49.55   9.653%   $54.3331   $54.33   $54.35   $54.30  
  Purchase #7 $183.40   5.371%   $193.2504   $193.25   $193.25   $193.30  
  7 purchase totals = $1,029.33       $1,102.6029   $1,102.60   $1,102.60   $1,102.70