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 $216.70   4.455%   $226.354   $226.35   $226.35   $226.40  
  Purchase #2 $98.37   5.307%   $103.5905   $103.59   $103.60   $103.60  
  Purchase #3 $32.69   13.842%   $37.2149   $37.21   $37.20   $37.20  
  Purchase #4 $178.28   13.849%   $202.97   $202.97   $202.95   $203.00  
  Purchase #5 $227.73   5.261%   $239.7109   $239.71   $239.70   $239.70  
  Purchase #6 $173.51   8.698%   $188.6019   $188.60   $188.60   $188.60  
  Purchase #7 $176.57   11.225%   $196.39   $196.39   $196.40   $196.40  
  7 purchase totals = $1,103.85       $1,194.8322   $1,194.82   $1,194.80   $1,194.90