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 $246.26   6.567%   $262.4319   $262.43   $262.45   $262.40  
  Purchase #2 $106.80   6.748%   $114.0069   $114.01   $114.00   $114.00  
  Purchase #3 $167.92   3.768%   $174.2472   $174.25   $174.25   $174.20  
  Purchase #4 $68.88   10.341%   $76.0029   $76.00   $76.00   $76.00  
  Purchase #5 $203.52   4.517%   $212.713   $212.71   $212.70   $212.70  
  Purchase #6 $48.96   8.132%   $52.9414   $52.94   $52.95   $52.90  
  Purchase #7 $119.62   3.438%   $123.7325   $123.73   $123.75   $123.70  
  7 purchase totals = $961.96       $1,016.0758   $1,016.07   $1,016.10   $1,015.90