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 $146.95   5.193%   $154.5811   $154.58   $154.60   $154.60  
  Purchase #2 $153.77   6.243%   $163.3699   $163.37   $163.35   $163.40  
  Purchase #3 $237.46   12.403%   $266.9122   $266.91   $266.90   $266.90  
  Purchase #4 $92.39   3.230%   $95.3742   $95.37   $95.35   $95.40  
  Purchase #5 $74.69   3.494%   $77.2997   $77.30   $77.30   $77.30  
  Purchase #6 $222.52   5.743%   $235.2993   $235.30   $235.30   $235.30  
  Purchase #7 $51.59   11.325%   $57.4326   $57.43   $57.45   $57.40  
  7 purchase totals = $979.37       $1,050.2690   $1,050.26   $1,050.25   $1,050.30