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 $60.96   3.107%   $62.854   $62.85   $62.85   $62.90  
  Purchase #2 $217.57   6.437%   $231.575   $231.58   $231.60   $231.60  
  Purchase #3 $69.48   3.746%   $72.0827   $72.08   $72.10   $72.10  
  Purchase #4 $231.29   8.671%   $251.3452   $251.35   $251.35   $251.30  
  Purchase #5 $55.95   13.384%   $63.4383   $63.44   $63.45   $63.40  
  Purchase #6 $15.73   12.463%   $17.6904   $17.69   $17.70   $17.70  
  Purchase #7 $117.43   4.483%   $122.6944   $122.69   $122.70   $122.70  
  7 purchase totals = $768.41       $821.6800   $821.68   $821.75   $821.70