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 $24.76   4.854%   $25.9619   $25.96   $25.95   $26.00  
  Purchase #2 $179.84   9.574%   $197.0579   $197.06   $197.05   $197.10  
  Purchase #3 $116.27   3.631%   $120.4918   $120.49   $120.50   $120.50  
  Purchase #4 $225.53   10.637%   $249.5196   $249.52   $249.50   $249.50  
  Purchase #5 $103.64   9.777%   $113.7729   $113.77   $113.75   $113.80  
  Purchase #6 $223.71   9.247%   $244.3965   $244.40   $244.40   $244.40  
  Purchase #7 $198.36   4.854%   $207.9884   $207.99   $208.00   $208.00  
  7 purchase totals = $1,072.11       $1,159.1890   $1,159.19   $1,159.15   $1,159.30