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 $64.31   7.327%   $69.022   $69.02   $69.00   $69.00  
  Purchase #2 $208.75   7.554%   $224.519   $224.52   $224.50   $224.50  
  Purchase #3 $167.61   5.668%   $177.1101   $177.11   $177.10   $177.10  
  Purchase #4 $189.61   4.365%   $197.8865   $197.89   $197.90   $197.90  
  Purchase #5 $133.66   11.276%   $148.7315   $148.73   $148.75   $148.70  
  Purchase #6 $97.56   5.522%   $102.9473   $102.95   $102.95   $102.90  
  Purchase #7 $163.97   12.260%   $184.0727   $184.07   $184.05   $184.10  
  7 purchase totals = $1,025.47       $1,104.2891   $1,104.29   $1,104.25   $1,104.20