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 $214.72   9.736%   $235.6251   $235.63   $235.65   $235.60  
  Purchase #2 $201.99   13.142%   $228.5355   $228.54   $228.55   $228.50  
  Purchase #3 $53.27   13.462%   $60.4412   $60.44   $60.45   $60.40  
  Purchase #4 $159.59   10.170%   $175.8203   $175.82   $175.80   $175.80  
  Purchase #5 $114.40   13.305%   $129.6209   $129.62   $129.60   $129.60  
  Purchase #6 $39.48   4.273%   $41.167   $41.17   $41.15   $41.20  
  Purchase #7 $202.98   5.312%   $213.7623   $213.76   $213.75   $213.80  
  7 purchase totals = $986.43       $1,084.9723   $1,084.98   $1,084.95   $1,084.90