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 $233.80   5.483%   $246.6193   $246.62   $246.60   $246.60  
  Purchase #2 $38.52   8.369%   $41.7437   $41.74   $41.75   $41.70  
  Purchase #3 $245.28   11.538%   $273.5804   $273.58   $273.60   $273.60  
  Purchase #4 $208.81   9.748%   $229.1648   $229.16   $229.15   $229.20  
  Purchase #5 $191.98   5.113%   $201.7959   $201.80   $201.80   $201.80  
  Purchase #6 $191.82   3.325%   $198.198   $198.20   $198.20   $198.20  
  Purchase #7 $180.93   8.113%   $195.6089   $195.61   $195.60   $195.60  
  7 purchase totals = $1,291.14       $1,386.7110   $1,386.71   $1,386.70   $1,386.70