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 $92.25   3.143%   $95.1494   $95.15   $95.15   $95.10  
  Purchase #2 $145.87   11.818%   $163.1089   $163.11   $163.10   $163.10  
  Purchase #3 $179.83   4.213%   $187.4062   $187.41   $187.40   $187.40  
  Purchase #4 $14.48   10.678%   $16.0262   $16.03   $16.05   $16.00  
  Purchase #5 $66.25   8.150%   $71.6494   $71.65   $71.65   $71.60  
  Purchase #6 $176.84   4.285%   $184.4176   $184.42   $184.40   $184.40  
  Purchase #7 $51.65   12.469%   $58.0902   $58.09   $58.10   $58.10  
  7 purchase totals = $727.17       $775.8479   $775.86   $775.85   $775.70