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 $118.43   5.644%   $125.1142   $125.11   $125.10   $125.10  
  Purchase #2 $74.60   3.216%   $76.9991   $77.00   $77.00   $77.00  
  Purchase #3 $250.59   8.239%   $271.2361   $271.24   $271.25   $271.20  
  Purchase #4 $152.60   13.797%   $173.6542   $173.65   $173.65   $173.70  
  Purchase #5 $124.30   10.786%   $137.707   $137.71   $137.70   $137.70  
  Purchase #6 $176.37   6.115%   $187.155   $187.16   $187.15   $187.20  
  Purchase #7 $87.52   11.774%   $97.8246   $97.82   $97.80   $97.80  
  7 purchase totals = $984.41       $1,069.6902   $1,069.69   $1,069.65   $1,069.70