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 $119.88   5.112%   $126.0083   $126.01   $126.00   $126.00  
  Purchase #2 $164.90   12.589%   $185.6593   $185.66   $185.65   $185.70  
  Purchase #3 $33.46   3.328%   $34.5735   $34.57   $34.55   $34.60  
  Purchase #4 $56.85   3.407%   $58.7869   $58.79   $58.80   $58.80  
  Purchase #5 $122.31   5.159%   $128.62   $128.62   $128.60   $128.60  
  Purchase #6 $197.45   6.280%   $209.8499   $209.85   $209.85   $209.80  
  Purchase #7 $230.44   3.637%   $238.8211   $238.82   $238.80   $238.80  
  7 purchase totals = $925.29       $982.3190   $982.32   $982.25   $982.30