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 $63.31   13.667%   $71.9626   $71.96   $71.95   $72.00  
  Purchase #2 $225.95   5.791%   $239.0348   $239.03   $239.05   $239.00  
  Purchase #3 $194.64   8.844%   $211.854   $211.85   $211.85   $211.90  
  Purchase #4 $221.59   11.238%   $246.4923   $246.49   $246.50   $246.50  
  Purchase #5 $90.31   5.730%   $95.4848   $95.48   $95.50   $95.50  
  Purchase #6 $223.91   12.180%   $251.1822   $251.18   $251.20   $251.20  
  Purchase #7 $36.56   7.775%   $39.4025   $39.40   $39.40   $39.40  
  7 purchase totals = $1,056.27       $1,155.4132   $1,155.39   $1,155.45   $1,155.50