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 $161.50   3.434%   $167.0459   $167.05   $167.05   $167.00  
  Purchase #2 $158.72   12.787%   $179.0155   $179.02   $179.00   $179.00  
  Purchase #3 $184.98   5.782%   $195.6755   $195.68   $195.70   $195.70  
  Purchase #4 $90.82   4.137%   $94.5772   $94.58   $94.60   $94.60  
  Purchase #5 $162.26   11.244%   $180.5045   $180.50   $180.50   $180.50  
  Purchase #6 $187.94   7.214%   $201.498   $201.50   $201.50   $201.50  
  Purchase #7 $110.69   3.775%   $114.8685   $114.87   $114.85   $114.90  
  7 purchase totals = $1,056.91       $1,133.1851   $1,133.20   $1,133.20   $1,133.20