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 $103.84   13.672%   $118.037   $118.04   $118.05   $118.00  
  Purchase #2 $235.38   7.163%   $252.2403   $252.24   $252.25   $252.20  
  Purchase #3 $42.37   5.322%   $44.6249   $44.62   $44.60   $44.60  
  Purchase #4 $207.61   13.873%   $236.4117   $236.41   $236.40   $236.40  
  Purchase #5 $230.42   11.795%   $257.598   $257.60   $257.60   $257.60  
  Purchase #6 $113.63   6.345%   $120.8398   $120.84   $120.85   $120.80  
  Purchase #7 $160.67   3.196%   $165.805   $165.81   $165.80   $165.80  
  7 purchase totals = $1,093.92       $1,195.5567   $1,195.56   $1,195.55   $1,195.40