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 $72.72   5.681%   $76.8512   $76.85   $76.85   $76.90  
  Purchase #2 $237.89   6.562%   $253.5003   $253.50   $253.50   $253.50  
  Purchase #3 $102.26   12.132%   $114.6662   $114.67   $114.65   $114.70  
  Purchase #4 $202.30   8.751%   $220.0033   $220.00   $220.00   $220.00  
  Purchase #5 $174.79   10.162%   $192.5522   $192.55   $192.55   $192.60  
  Purchase #6 $9.28   5.606%   $9.8002   $9.80   $9.80   $9.80  
  Purchase #7 $184.59   8.644%   $200.546   $200.55   $200.55   $200.50  
  7 purchase totals = $983.83       $1,067.9194   $1,067.92   $1,067.90   $1,068.00