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 $22.48   5.698%   $23.7609   $23.76   $23.75   $23.80  
  Purchase #2 $175.34   11.366%   $195.2691   $195.27   $195.25   $195.30  
  Purchase #3 $135.84   5.658%   $143.5258   $143.53   $143.55   $143.50  
  Purchase #4 $198.53   12.809%   $223.9597   $223.96   $223.95   $224.00  
  Purchase #5 $49.63   8.280%   $53.7394   $53.74   $53.75   $53.70  
  Purchase #6 $230.74   6.866%   $246.5826   $246.58   $246.60   $246.60  
  Purchase #7 $211.31   11.269%   $235.1225   $235.12   $235.10   $235.10  
  7 purchase totals = $1,023.87       $1,121.9600   $1,121.96   $1,121.95   $1,122.00