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 $59.59   3.422%   $61.6292   $61.63   $61.65   $61.60  
  Purchase #2 $243.32   10.313%   $268.4136   $268.41   $268.40   $268.40  
  Purchase #3 $169.83   12.548%   $191.1403   $191.14   $191.15   $191.10  
  Purchase #4 $147.57   8.484%   $160.0898   $160.09   $160.10   $160.10  
  Purchase #5 $91.87   12.455%   $103.3124   $103.31   $103.30   $103.30  
  Purchase #6 $25.96   3.743%   $26.9317   $26.93   $26.95   $26.90  
  Purchase #7 $225.51   9.565%   $247.08   $247.08   $247.10   $247.10  
  7 purchase totals = $963.65       $1,058.5970   $1,058.59   $1,058.65   $1,058.50