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 $146.51   4.216%   $152.6869   $152.69   $152.70   $152.70  
  Purchase #2 $148.71   8.588%   $161.4812   $161.48   $161.50   $161.50  
  Purchase #3 $85.89   9.402%   $93.9654   $93.97   $93.95   $94.00  
  Purchase #4 $179.85   7.474%   $193.292   $193.29   $193.30   $193.30  
  Purchase #5 $170.54   7.864%   $183.9513   $183.95   $183.95   $184.00  
  Purchase #6 $184.94   11.176%   $205.6089   $205.61   $205.60   $205.60  
  Purchase #7 $65.81   5.136%   $69.19   $69.19   $69.20   $69.20  
  7 purchase totals = $982.25       $1,060.1757   $1,060.18   $1,060.20   $1,060.30