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 $33.55   6.230%   $35.6402   $35.64   $35.65   $35.60  
  Purchase #2 $157.45   5.689%   $166.4073   $166.41   $166.40   $166.40  
  Purchase #3 $244.93   9.416%   $267.9926   $267.99   $268.00   $268.00  
  Purchase #4 $122.70   9.458%   $134.305   $134.31   $134.30   $134.30  
  Purchase #5 $234.58   3.559%   $242.9287   $242.93   $242.95   $242.90  
  Purchase #6 $205.45   4.819%   $215.3506   $215.35   $215.35   $215.40  
  Purchase #7 $102.82   8.359%   $111.4147   $111.41   $111.40   $111.40  
  7 purchase totals = $1,101.48       $1,174.0391   $1,174.04   $1,174.05   $1,174.00