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 $84.49   11.667%   $94.3474   $94.35   $94.35   $94.30  
  Purchase #2 $190.56   9.142%   $207.981   $207.98   $208.00   $208.00  
  Purchase #3 $248.47   9.253%   $271.4609   $271.46   $271.45   $271.50  
  Purchase #4 $133.60   10.413%   $147.5118   $147.51   $147.50   $147.50  
  Purchase #5 $109.37   11.603%   $122.0602   $122.06   $122.05   $122.10  
  Purchase #6 $176.74   9.616%   $193.7353   $193.74   $193.75   $193.70  
  Purchase #7 $115.50   10.456%   $127.5767   $127.58   $127.60   $127.60  
  7 purchase totals = $1,058.73       $1,164.6733   $1,164.68   $1,164.70   $1,164.70