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 $58.61   8.607%   $63.6546   $63.65   $63.65   $63.70  
  Purchase #2 $208.39   7.747%   $224.534   $224.53   $224.55   $224.50  
  Purchase #3 $53.83   6.705%   $57.4393   $57.44   $57.45   $57.40  
  Purchase #4 $232.27   6.666%   $247.7531   $247.75   $247.75   $247.80  
  Purchase #5 $66.80   3.131%   $68.8915   $68.89   $68.90   $68.90  
  Purchase #6 $190.85   13.263%   $216.1624   $216.16   $216.15   $216.20  
  Purchase #7 $59.45   5.637%   $62.8012   $62.80   $62.80   $62.80  
  7 purchase totals = $870.20       $941.2361   $941.22   $941.25   $941.30