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 $60.30   11.606%   $67.2984   $67.30   $67.30   $67.30  
  Purchase #2 $216.47   6.229%   $229.9539   $229.95   $229.95   $230.00  
  Purchase #3 $190.77   4.320%   $199.0113   $199.01   $199.00   $199.00  
  Purchase #4 $248.59   6.555%   $264.8851   $264.89   $264.90   $264.90  
  Purchase #5 $114.82   8.873%   $125.008   $125.01   $125.00   $125.00  
  Purchase #6 $203.44   6.678%   $217.0257   $217.03   $217.05   $217.00  
  Purchase #7 $26.59   3.726%   $27.5807   $27.58   $27.60   $27.60  
  7 purchase totals = $1,060.98       $1,130.7631   $1,130.77   $1,130.80   $1,130.80