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 $141.95   7.620%   $152.7666   $152.77   $152.75   $152.80  
  Purchase #2 $235.85   11.433%   $262.8147   $262.81   $262.80   $262.80  
  Purchase #3 $238.88   3.477%   $247.1859   $247.19   $247.20   $247.20  
  Purchase #4 $161.32   7.692%   $173.7287   $173.73   $173.75   $173.70  
  Purchase #5 $187.76   5.135%   $197.4015   $197.40   $197.40   $197.40  
  Purchase #6 $247.27   12.273%   $277.6174   $277.62   $277.60   $277.60  
  Purchase #7 $103.45   9.187%   $112.954   $112.95   $112.95   $113.00  
  7 purchase totals = $1,316.48       $1,424.4688   $1,424.47   $1,424.45   $1,424.50