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 $61.86   6.255%   $65.7293   $65.73   $65.75   $65.70  
  Purchase #2 $188.49   7.289%   $202.229   $202.23   $202.25   $202.20  
  Purchase #3 $223.52   3.855%   $232.1367   $232.14   $232.15   $232.10  
  Purchase #4 $162.80   12.722%   $183.5114   $183.51   $183.50   $183.50  
  Purchase #5 $127.55   8.445%   $138.3216   $138.32   $138.30   $138.30  
  Purchase #6 $41.49   8.289%   $44.9291   $44.93   $44.95   $44.90  
  Purchase #7 $96.42   5.617%   $101.8359   $101.84   $101.85   $101.80  
  7 purchase totals = $902.13       $968.6930   $968.70   $968.75   $968.50