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 $94.26   4.678%   $98.6695   $98.67   $98.65   $98.70  
  Purchase #2 $218.30   6.255%   $231.9547   $231.95   $231.95   $232.00  
  Purchase #3 $120.81   5.680%   $127.672   $127.67   $127.65   $127.70  
  Purchase #4 $84.25   4.631%   $88.1516   $88.15   $88.15   $88.20  
  Purchase #5 $209.69   5.864%   $221.9862   $221.99   $222.00   $222.00  
  Purchase #6 $245.73   11.108%   $273.0257   $273.03   $273.05   $273.00  
  Purchase #7 $119.36   6.131%   $126.678   $126.68   $126.70   $126.70  
  7 purchase totals = $1,092.40       $1,168.1377   $1,168.14   $1,168.15   $1,168.30