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 $215.37   4.818%   $225.7465   $225.75   $225.75   $225.70  
  Purchase #2 $90.68   9.521%   $99.3136   $99.31   $99.30   $99.30  
  Purchase #3 $227.31   6.633%   $242.3875   $242.39   $242.40   $242.40  
  Purchase #4 $113.39   6.451%   $120.7048   $120.70   $120.70   $120.70  
  Purchase #5 $216.75   10.325%   $239.1294   $239.13   $239.15   $239.10  
  Purchase #6 $182.87   5.687%   $193.2698   $193.27   $193.25   $193.30  
  Purchase #7 $55.91   10.619%   $61.8471   $61.85   $61.85   $61.80  
  7 purchase totals = $1,102.28       $1,182.3987   $1,182.40   $1,182.40   $1,182.30