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 $32.89   7.385%   $35.3189   $35.32   $35.30   $35.30  
  Purchase #2 $174.63   10.555%   $193.0622   $193.06   $193.05   $193.10  
  Purchase #3 $58.74   9.152%   $64.1159   $64.12   $64.10   $64.10  
  Purchase #4 $239.88   11.226%   $266.8089   $266.81   $266.80   $266.80  
  Purchase #5 $52.40   6.226%   $55.6624   $55.66   $55.65   $55.70  
  Purchase #6 $181.71   13.115%   $205.5413   $205.54   $205.55   $205.50  
  Purchase #7 $193.74   9.345%   $211.845   $211.85   $211.85   $211.80  
  7 purchase totals = $933.99       $1,032.3546   $1,032.36   $1,032.30   $1,032.30