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 $168.37   5.463%   $177.5681   $177.57   $177.55   $177.60  
  Purchase #2 $240.82   11.546%   $268.6251   $268.63   $268.65   $268.60  
  Purchase #3 $20.97   8.348%   $22.7206   $22.72   $22.70   $22.70  
  Purchase #4 $111.68   5.240%   $117.532   $117.53   $117.55   $117.50  
  Purchase #5 $31.47   10.142%   $34.6617   $34.66   $34.65   $34.70  
  Purchase #6 $250.82   13.207%   $283.9458   $283.95   $283.95   $283.90  
  Purchase #7 $162.61   4.585%   $170.0657   $170.07   $170.05   $170.10  
  7 purchase totals = $986.74       $1,075.1190   $1,075.13   $1,075.10   $1,075.10