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 $195.43   5.284%   $205.7565   $205.76   $205.75   $205.80  
  Purchase #2 $159.94   8.121%   $172.9287   $172.93   $172.95   $172.90  
  Purchase #3 $23.60   10.796%   $26.1479   $26.15   $26.15   $26.10  
  Purchase #4 $207.51   11.592%   $231.5646   $231.56   $231.55   $231.60  
  Purchase #5 $177.57   6.597%   $189.2843   $189.28   $189.30   $189.30  
  Purchase #6 $214.28   8.415%   $232.3117   $232.31   $232.30   $232.30  
  Purchase #7 $208.86   4.490%   $218.2378   $218.24   $218.25   $218.20  
  7 purchase totals = $1,187.19       $1,276.2315   $1,276.23   $1,276.25   $1,276.20