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 $56.40   10.395%   $62.2628   $62.26   $62.25   $62.30  
  Purchase #2 $172.87   8.782%   $188.0514   $188.05   $188.05   $188.10  
  Purchase #3 $165.26   11.664%   $184.5359   $184.54   $184.55   $184.50  
  Purchase #4 $213.99   5.855%   $226.5191   $226.52   $226.50   $226.50  
  Purchase #5 $244.72   7.670%   $263.49   $263.49   $263.50   $263.50  
  Purchase #6 $155.39   9.783%   $170.5918   $170.59   $170.60   $170.60  
  Purchase #7 $7.60   10.120%   $8.3691   $8.37   $8.35   $8.40  
  7 purchase totals = $1,016.23       $1,103.8201   $1,103.82   $1,103.80   $1,103.90