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 $176.88   4.745%   $185.273   $185.27   $185.25   $185.30  
  Purchase #2 $191.26   5.386%   $201.5613   $201.56   $201.55   $201.60  
  Purchase #3 $165.28   5.788%   $174.8464   $174.85   $174.85   $174.80  
  Purchase #4 $186.84   5.817%   $197.7085   $197.71   $197.70   $197.70  
  Purchase #5 $72.33   5.447%   $76.2698   $76.27   $76.25   $76.30  
  Purchase #6 $6.61   6.183%   $7.0187   $7.02   $7.00   $7.00  
  Purchase #7 $244.66   7.799%   $263.741   $263.74   $263.75   $263.70  
  7 purchase totals = $1,043.86       $1,106.4187   $1,106.42   $1,106.35   $1,106.40