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 $64.58   5.239%   $67.9633   $67.96   $67.95   $68.00  
  Purchase #2 $73.41   3.127%   $75.7055   $75.71   $75.70   $75.70  
  Purchase #3 $163.59   5.216%   $172.1229   $172.12   $172.10   $172.10  
  Purchase #4 $64.68   9.364%   $70.7366   $70.74   $70.75   $70.70  
  Purchase #5 $38.88   8.683%   $42.256   $42.26   $42.25   $42.30  
  Purchase #6 $222.44   3.674%   $230.6124   $230.61   $230.60   $230.60  
  Purchase #7 $133.67   7.103%   $143.1646   $143.16   $143.15   $143.20  
  7 purchase totals = $761.25       $802.5613   $802.56   $802.50   $802.60