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 $66.89   13.551%   $75.9543   $75.95   $75.95   $76.00  
  Purchase #2 $219.63   7.517%   $236.1396   $236.14   $236.15   $236.10  
  Purchase #3 $206.77   7.819%   $222.9373   $222.94   $222.95   $222.90  
  Purchase #4 $221.44   11.300%   $246.4627   $246.46   $246.45   $246.50  
  Purchase #5 $186.36   6.449%   $198.3784   $198.38   $198.40   $198.40  
  Purchase #6 $5.66   6.125%   $6.0067   $6.01   $6.00   $6.00  
  Purchase #7 $78.53   11.186%   $87.3144   $87.31   $87.30   $87.30  
  7 purchase totals = $985.28       $1,073.1934   $1,073.19   $1,073.20   $1,073.20