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 $63.95   8.812%   $69.5853   $69.59   $69.60   $69.60  
  Purchase #2 $213.48   3.816%   $221.6264   $221.63   $221.65   $221.60  
  Purchase #3 $230.91   11.562%   $257.6078   $257.61   $257.60   $257.60  
  Purchase #4 $54.41   8.396%   $58.9783   $58.98   $59.00   $59.00  
  Purchase #5 $96.77   5.326%   $101.924   $101.92   $101.90   $101.90  
  Purchase #6 $231.88   13.852%   $264   $264.00   $264.00   $264.00  
  Purchase #7 $135.47   6.147%   $143.7973   $143.80   $143.80   $143.80  
  7 purchase totals = $1,026.87       $1,117.5191   $1,117.53   $1,117.55   $1,117.50