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 $193.74   3.549%   $200.6158   $200.62   $200.60   $200.60  
  Purchase #2 $204.88   11.381%   $228.1974   $228.20   $228.20   $228.20  
  Purchase #3 $102.74   12.543%   $115.6267   $115.63   $115.65   $115.60  
  Purchase #4 $77.97   10.675%   $86.2933   $86.29   $86.30   $86.30  
  Purchase #5 $147.80   9.659%   $162.076   $162.08   $162.10   $162.10  
  Purchase #6 $69.75   4.597%   $72.9564   $72.96   $72.95   $73.00  
  Purchase #7 $167.91   5.649%   $177.3952   $177.40   $177.40   $177.40  
  7 purchase totals = $964.79       $1,043.1608   $1,043.18   $1,043.20   $1,043.20