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 $208.37   8.494%   $226.0689   $226.07   $226.05   $226.10  
  Purchase #2 $200.45   11.666%   $223.8345   $223.83   $223.85   $223.80  
  Purchase #3 $214.29   3.388%   $221.5501   $221.55   $221.55   $221.60  
  Purchase #4 $24.86   6.166%   $26.3929   $26.39   $26.40   $26.40  
  Purchase #5 $150.35   8.385%   $162.9568   $162.96   $162.95   $163.00  
  Purchase #6 $43.68   6.671%   $46.5939   $46.59   $46.60   $46.60  
  Purchase #7 $201.35   6.742%   $214.925   $214.93   $214.95   $214.90  
  7 purchase totals = $1,043.35       $1,122.3221   $1,122.32   $1,122.35   $1,122.40