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 $32.54   8.465%   $35.2945   $35.29   $35.30   $35.30  
  Purchase #2 $110.48   7.640%   $118.9207   $118.92   $118.90   $118.90  
  Purchase #3 $112.25   3.734%   $116.4414   $116.44   $116.45   $116.40  
  Purchase #4 $166.86   8.704%   $181.3835   $181.38   $181.40   $181.40  
  Purchase #5 $236.34   10.557%   $261.2904   $261.29   $261.30   $261.30  
  Purchase #6 $200.48   5.270%   $211.0453   $211.05   $211.05   $211.00  
  Purchase #7 $163.68   6.810%   $174.8266   $174.83   $174.85   $174.80  
  7 purchase totals = $1,022.63       $1,099.2024   $1,099.20   $1,099.25   $1,099.10