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 $182.86   6.127%   $194.0638   $194.06   $194.05   $194.10  
  Purchase #2 $219.94   6.233%   $233.6489   $233.65   $233.65   $233.60  
  Purchase #3 $115.48   11.355%   $128.5928   $128.59   $128.60   $128.60  
  Purchase #4 $218.78   10.229%   $241.159   $241.16   $241.15   $241.20  
  Purchase #5 $196.83   5.775%   $208.1969   $208.20   $208.20   $208.20  
  Purchase #6 $151.50   6.506%   $161.3566   $161.36   $161.35   $161.40  
  Purchase #7 $234.31   11.366%   $260.9417   $260.94   $260.95   $260.90  
  7 purchase totals = $1,319.70       $1,427.9597   $1,427.96   $1,427.95   $1,428.00