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 $23.50   11.535%   $26.2107   $26.21   $26.20   $26.20  
  Purchase #2 $193.61   8.655%   $210.3669   $210.37   $210.35   $210.40  
  Purchase #3 $225.44   8.236%   $244.0072   $244.01   $244.00   $244.00  
  Purchase #4 $61.59   10.690%   $68.174   $68.17   $68.15   $68.20  
  Purchase #5 $201.32   5.144%   $211.6759   $211.68   $211.70   $211.70  
  Purchase #6 $215.74   5.571%   $227.7589   $227.76   $227.75   $227.80  
  Purchase #7 $226.57   11.346%   $252.2766   $252.28   $252.30   $252.30  
  7 purchase totals = $1,147.77       $1,240.4702   $1,240.48   $1,240.45   $1,240.60