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 $147.47   10.693%   $163.239   $163.24   $163.25   $163.20  
  Purchase #2 $172.38   3.210%   $177.9134   $177.91   $177.90   $177.90  
  Purchase #3 $210.31   10.338%   $232.0518   $232.05   $232.05   $232.10  
  Purchase #4 $23.29   10.153%   $25.6546   $25.65   $25.65   $25.70  
  Purchase #5 $85.89   12.462%   $96.5936   $96.59   $96.60   $96.60  
  Purchase #6 $92.69   13.207%   $104.9316   $104.93   $104.95   $104.90  
  Purchase #7 $198.88   5.821%   $210.4568   $210.46   $210.45   $210.50  
  7 purchase totals = $930.91       $1,010.8408   $1,010.83   $1,010.85   $1,010.90