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 $58.31   5.494%   $61.5136   $61.51   $61.50   $61.50  
  Purchase #2 $224.84   4.608%   $235.2006   $235.20   $235.20   $235.20  
  Purchase #3 $8.35   11.413%   $9.303   $9.30   $9.30   $9.30  
  Purchase #4 $53.57   11.309%   $59.6282   $59.63   $59.65   $59.60  
  Purchase #5 $161.49   13.541%   $183.3574   $183.36   $183.35   $183.40  
  Purchase #6 $5.46   3.826%   $5.6689   $5.67   $5.65   $5.70  
  Purchase #7 $235.82   4.621%   $246.7172   $246.72   $246.70   $246.70  
  7 purchase totals = $747.84       $801.3889   $801.39   $801.35   $801.40