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 $97.27   8.231%   $105.2763   $105.28   $105.30   $105.30  
  Purchase #2 $150.47   4.540%   $157.3013   $157.30   $157.30   $157.30  
  Purchase #3 $56.70   5.234%   $59.6677   $59.67   $59.65   $59.70  
  Purchase #4 $145.81   6.102%   $154.7073   $154.71   $154.70   $154.70  
  Purchase #5 $198.44   6.275%   $210.8921   $210.89   $210.90   $210.90  
  Purchase #6 $212.57   4.160%   $221.4129   $221.41   $221.40   $221.40  
  Purchase #7 $32.81   3.701%   $34.0243   $34.02   $34.00   $34.00  
  7 purchase totals = $894.07       $943.2819   $943.28   $943.25   $943.30