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 $212.70   11.746%   $237.6837   $237.68   $237.70   $237.70  
  Purchase #2 $74.52   3.213%   $76.9143   $76.91   $76.90   $76.90  
  Purchase #3 $95.71   12.750%   $107.913   $107.91   $107.90   $107.90  
  Purchase #4 $127.80   6.501%   $136.1083   $136.11   $136.10   $136.10  
  Purchase #5 $40.28   4.801%   $42.2138   $42.21   $42.20   $42.20  
  Purchase #6 $169.84   12.582%   $191.2093   $191.21   $191.20   $191.20  
  Purchase #7 $203.50   9.543%   $222.92   $222.92   $222.90   $222.90  
  7 purchase totals = $924.35       $1,014.9624   $1,014.95   $1,014.90   $1,014.90