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 $58.54   5.767%   $61.916   $61.92   $61.90   $61.90  
  Purchase #2 $241.61   13.230%   $273.575   $273.58   $273.60   $273.60  
  Purchase #3 $71.36   8.170%   $77.1901   $77.19   $77.20   $77.20  
  Purchase #4 $136.82   8.141%   $147.9585   $147.96   $147.95   $148.00  
  Purchase #5 $8.47   8.680%   $9.2052   $9.21   $9.20   $9.20  
  Purchase #6 $129.27   13.813%   $147.1261   $147.13   $147.15   $147.10  
  Purchase #7 $171.69   12.864%   $193.7762   $193.78   $193.80   $193.80  
  7 purchase totals = $817.76       $910.7471   $910.77   $910.80   $910.80