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 $196.60   7.451%   $211.2487   $211.25   $211.25   $211.20  
  Purchase #2 $143.61   8.144%   $155.3056   $155.31   $155.30   $155.30  
  Purchase #3 $32.52   5.146%   $34.1935   $34.19   $34.20   $34.20  
  Purchase #4 $172.74   13.762%   $196.5125   $196.51   $196.50   $196.50  
  Purchase #5 $206.99   4.598%   $216.5074   $216.51   $216.50   $216.50  
  Purchase #6 $206.72   9.354%   $226.0566   $226.06   $226.05   $226.10  
  Purchase #7 $172.35   9.208%   $188.22   $188.22   $188.20   $188.20  
  7 purchase totals = $1,131.53       $1,228.0443   $1,228.05   $1,228.00   $1,228.00