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 $94.89   8.153%   $102.6264   $102.63   $102.65   $102.60  
  Purchase #2 $122.72   9.117%   $133.9084   $133.91   $133.90   $133.90  
  Purchase #3 $106.54   6.585%   $113.5557   $113.56   $113.55   $113.60  
  Purchase #4 $113.56   7.325%   $121.8783   $121.88   $121.90   $121.90  
  Purchase #5 $103.94   11.212%   $115.5938   $115.59   $115.60   $115.60  
  Purchase #6 $15.56   7.859%   $16.7829   $16.78   $16.80   $16.80  
  Purchase #7 $92.70   5.249%   $97.5658   $97.57   $97.55   $97.60  
  7 purchase totals = $649.91       $701.9113   $701.92   $701.95   $702.00