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 $190.86   5.816%   $201.9604   $201.96   $201.95   $202.00  
  Purchase #2 $182.38   11.292%   $202.9743   $202.97   $202.95   $203.00  
  Purchase #3 $166.99   11.467%   $186.1387   $186.14   $186.15   $186.10  
  Purchase #4 $81.79   8.546%   $88.7798   $88.78   $88.80   $88.80  
  Purchase #5 $60.92   7.193%   $65.302   $65.30   $65.30   $65.30  
  Purchase #6 $193.59   11.389%   $215.638   $215.64   $215.65   $215.60  
  Purchase #7 $160.99   4.844%   $168.7884   $168.79   $168.80   $168.80  
  7 purchase totals = $1,037.52       $1,129.5816   $1,129.58   $1,129.60   $1,129.60