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 $85.48   11.756%   $95.529   $95.53   $95.55   $95.50  
  Purchase #2 $32.47   9.780%   $35.6456   $35.65   $35.65   $35.60  
  Purchase #3 $111.81   4.257%   $116.5698   $116.57   $116.55   $116.60  
  Purchase #4 $210.32   10.211%   $231.7958   $231.80   $231.80   $231.80  
  Purchase #5 $143.78   12.386%   $161.5886   $161.59   $161.60   $161.60  
  Purchase #6 $91.94   4.713%   $96.2731   $96.27   $96.25   $96.30  
  Purchase #7 $161.69   13.786%   $183.9806   $183.98   $184.00   $184.00  
  7 purchase totals = $837.49       $921.3825   $921.39   $921.40   $921.40