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 $84.99   12.424%   $95.5492   $95.55   $95.55   $95.50  
  Purchase #2 $105.25   7.643%   $113.2943   $113.29   $113.30   $113.30  
  Purchase #3 $65.73   5.279%   $69.1999   $69.20   $69.20   $69.20  
  Purchase #4 $242.51   4.384%   $253.1416   $253.14   $253.15   $253.10  
  Purchase #5 $39.34   10.686%   $43.5439   $43.54   $43.55   $43.50  
  Purchase #6 $182.53   7.356%   $195.9569   $195.96   $195.95   $196.00  
  Purchase #7 $231.89   10.598%   $256.4657   $256.47   $256.45   $256.50  
  7 purchase totals = $952.24       $1,027.1515   $1,027.15   $1,027.15   $1,027.10