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 $67.69   10.355%   $74.6993   $74.70   $74.70   $74.70  
  Purchase #2 $246.72   6.334%   $262.3472   $262.35   $262.35   $262.30  
  Purchase #3 $202.60   4.786%   $212.2964   $212.30   $212.30   $212.30  
  Purchase #4 $131.44   6.411%   $139.8666   $139.87   $139.85   $139.90  
  Purchase #5 $72.54   3.259%   $74.9041   $74.90   $74.90   $74.90  
  Purchase #6 $59.50   11.354%   $66.2556   $66.26   $66.25   $66.30  
  Purchase #7 $173.70   10.132%   $191.2993   $191.30   $191.30   $191.30  
  7 purchase totals = $954.19       $1,021.6685   $1,021.68   $1,021.65   $1,021.70