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 $233.78   8.333%   $253.2609   $253.26   $253.25   $253.30  
  Purchase #2 $197.31   8.613%   $214.3043   $214.30   $214.30   $214.30  
  Purchase #3 $24.62   3.676%   $25.525   $25.53   $25.55   $25.50  
  Purchase #4 $166.74   9.812%   $183.1005   $183.10   $183.10   $183.10  
  Purchase #5 $228.99   4.483%   $239.2556   $239.26   $239.25   $239.30  
  Purchase #6 $25.78   9.284%   $28.1734   $28.17   $28.15   $28.20  
  Purchase #7 $148.29   9.512%   $162.3953   $162.40   $162.40   $162.40  
  7 purchase totals = $1,025.51       $1,106.0150   $1,106.02   $1,106.00   $1,106.10