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 $98.74   7.501%   $106.1465   $106.15   $106.15   $106.10  
  Purchase #2 $173.58   11.302%   $193.198   $193.20   $193.20   $193.20  
  Purchase #3 $147.57   4.221%   $153.7989   $153.80   $153.80   $153.80  
  Purchase #4 $174.89   8.841%   $190.352   $190.35   $190.35   $190.40  
  Purchase #5 $53.57   5.738%   $56.6438   $56.64   $56.65   $56.60  
  Purchase #6 $186.81   13.237%   $211.538   $211.54   $211.55   $211.50  
  Purchase #7 $126.66   12.483%   $142.471   $142.47   $142.45   $142.50  
  7 purchase totals = $961.82       $1,054.1482   $1,054.15   $1,054.15   $1,054.10