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 $58.42   6.397%   $62.1571   $62.16   $62.15   $62.20  
  Purchase #2 $78.82   6.203%   $83.7092   $83.71   $83.70   $83.70  
  Purchase #3 $184.96   9.567%   $202.6551   $202.66   $202.65   $202.70  
  Purchase #4 $218.86   5.872%   $231.7115   $231.71   $231.70   $231.70  
  Purchase #5 $181.81   11.863%   $203.3781   $203.38   $203.40   $203.40  
  Purchase #6 $219.57   11.337%   $244.4627   $244.46   $244.45   $244.50  
  Purchase #7 $29.62   11.259%   $32.9549   $32.95   $32.95   $33.00  
  7 purchase totals = $972.06       $1,061.0286   $1,061.03   $1,061.00   $1,061.20