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 $191.51   10.185%   $211.0153   $211.02   $211.00   $211.00  
  Purchase #2 $178.34   13.691%   $202.7565   $202.76   $202.75   $202.80  
  Purchase #3 $77.92   7.570%   $83.8185   $83.82   $83.80   $83.80  
  Purchase #4 $182.25   7.710%   $196.3015   $196.30   $196.30   $196.30  
  Purchase #5 $55.31   8.615%   $60.075   $60.08   $60.10   $60.10  
  Purchase #6 $126.29   11.767%   $141.1505   $141.15   $141.15   $141.20  
  Purchase #7 $165.75   4.157%   $172.6402   $172.64   $172.65   $172.60  
  7 purchase totals = $977.37       $1,067.7575   $1,067.77   $1,067.75   $1,067.80