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 $187.69   11.573%   $209.4114   $209.41   $209.40   $209.40  
  Purchase #2 $90.73   5.764%   $95.9597   $95.96   $95.95   $96.00  
  Purchase #3 $22.79   6.364%   $24.2404   $24.24   $24.25   $24.20  
  Purchase #4 $237.90   7.146%   $254.9003   $254.90   $254.90   $254.90  
  Purchase #5 $204.41   4.691%   $213.9989   $214.00   $214.00   $214.00  
  Purchase #6 $128.74   4.666%   $134.747   $134.75   $134.75   $134.70  
  Purchase #7 $156.28   3.687%   $162.042   $162.04   $162.05   $162.00  
  7 purchase totals = $1,028.54       $1,095.2997   $1,095.30   $1,095.30   $1,095.20