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 $65.44   5.375%   $68.9574   $68.96   $68.95   $69.00  
  Purchase #2 $8.84   8.321%   $9.5756   $9.58   $9.60   $9.60  
  Purchase #3 $100.77   3.579%   $104.3766   $104.38   $104.40   $104.40  
  Purchase #4 $179.84   7.224%   $192.8316   $192.83   $192.85   $192.80  
  Purchase #5 $67.97   11.165%   $75.5589   $75.56   $75.55   $75.60  
  Purchase #6 $45.27   3.796%   $46.9884   $46.99   $47.00   $47.00  
  Purchase #7 $250.29   3.831%   $259.8786   $259.88   $259.90   $259.90  
  7 purchase totals = $718.42       $758.1671   $758.18   $758.25   $758.30