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 $59.99   11.145%   $66.6759   $66.68   $66.70   $66.70  
  Purchase #2 $232.95   6.513%   $248.122   $248.12   $248.10   $248.10  
  Purchase #3 $65.56   6.705%   $69.9558   $69.96   $69.95   $70.00  
  Purchase #4 $182.72   5.822%   $193.358   $193.36   $193.35   $193.40  
  Purchase #5 $55.57   3.119%   $57.3032   $57.30   $57.30   $57.30  
  Purchase #6 $160.63   7.146%   $172.1086   $172.11   $172.10   $172.10  
  Purchase #7 $136.80   3.333%   $141.3595   $141.36   $141.35   $141.40  
  7 purchase totals = $894.22       $948.8830   $948.89   $948.85   $949.00