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 $167.48   5.206%   $176.199   $176.20   $176.20   $176.20  
  Purchase #2 $65.89   11.667%   $73.5774   $73.58   $73.60   $73.60  
  Purchase #3 $245.55   7.540%   $264.0645   $264.06   $264.05   $264.10  
  Purchase #4 $39.85   12.162%   $44.6966   $44.70   $44.70   $44.70  
  Purchase #5 $164.64   12.362%   $184.9928   $184.99   $185.00   $185.00  
  Purchase #6 $139.72   3.758%   $144.9707   $144.97   $144.95   $145.00  
  Purchase #7 $106.56   12.153%   $119.5102   $119.51   $119.50   $119.50  
  7 purchase totals = $929.69       $1,008.0112   $1,008.01   $1,008.00   $1,008.10