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 $152.80   5.506%   $161.2132   $161.21   $161.20   $161.20  
  Purchase #2 $44.77   4.566%   $46.8142   $46.81   $46.80   $46.80  
  Purchase #3 $26.80   8.748%   $29.1445   $29.14   $29.15   $29.10  
  Purchase #4 $33.25   5.555%   $35.097   $35.10   $35.10   $35.10  
  Purchase #5 $140.25   4.800%   $146.982   $146.98   $147.00   $147.00  
  Purchase #6 $205.59   7.328%   $220.6556   $220.66   $220.65   $220.70  
  Purchase #7 $244.69   5.209%   $257.4359   $257.44   $257.45   $257.40  
  7 purchase totals = $848.15       $897.3424   $897.34   $897.35   $897.30