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 $58.94   6.475%   $62.7564   $62.76   $62.75   $62.80  
  Purchase #2 $226.74   10.602%   $250.779   $250.78   $250.80   $250.80  
  Purchase #3 $39.88   9.339%   $43.6044   $43.60   $43.60   $43.60  
  Purchase #4 $243.96   4.240%   $254.3039   $254.30   $254.30   $254.30  
  Purchase #5 $136.43   8.338%   $147.8055   $147.81   $147.80   $147.80  
  Purchase #6 $97.91   5.357%   $103.155   $103.16   $103.15   $103.20  
  Purchase #7 $12.92   12.526%   $14.5384   $14.54   $14.55   $14.50  
  7 purchase totals = $816.78       $876.9426   $876.95   $876.95   $877.00