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 $61.27   10.470%   $67.685   $67.69   $67.70   $67.70  
  Purchase #2 $157.28   12.849%   $177.4889   $177.49   $177.50   $177.50  
  Purchase #3 $79.26   4.638%   $82.9361   $82.94   $82.95   $82.90  
  Purchase #4 $247.72   11.640%   $276.5546   $276.55   $276.55   $276.60  
  Purchase #5 $72.26   10.193%   $79.6255   $79.63   $79.65   $79.60  
  Purchase #6 $200.65   5.209%   $211.1019   $211.10   $211.10   $211.10  
  Purchase #7 $230.48   13.821%   $262.3346   $262.33   $262.35   $262.30  
  7 purchase totals = $1,048.92       $1,157.7266   $1,157.73   $1,157.80   $1,157.70