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 $58.68   11.376%   $65.3554   $65.36   $65.35   $65.40  
  Purchase #2 $177.70   8.791%   $193.3216   $193.32   $193.30   $193.30  
  Purchase #3 $20.47   13.180%   $23.1679   $23.17   $23.15   $23.20  
  Purchase #4 $194.54   5.215%   $204.6853   $204.69   $204.70   $204.70  
  Purchase #5 $94.35   11.243%   $104.9578   $104.96   $104.95   $105.00  
  Purchase #6 $92.63   3.799%   $96.149   $96.15   $96.15   $96.10  
  Purchase #7 $65.30   13.475%   $74.0992   $74.10   $74.10   $74.10  
  7 purchase totals = $703.67       $761.7362   $761.75   $761.70   $761.80