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 $14.79   9.502%   $16.1953   $16.20   $16.20   $16.20  
  Purchase #2 $86.59   10.251%   $95.4663   $95.47   $95.45   $95.50  
  Purchase #3 $241.72   10.323%   $266.6728   $266.67   $266.65   $266.70  
  Purchase #4 $236.98   7.715%   $255.263   $255.26   $255.25   $255.30  
  Purchase #5 $88.70   7.688%   $95.5193   $95.52   $95.50   $95.50  
  Purchase #6 $195.71   11.746%   $218.6981   $218.70   $218.70   $218.70  
  Purchase #7 $232.55   11.508%   $259.3119   $259.31   $259.30   $259.30  
  7 purchase totals = $1,097.04       $1,207.1267   $1,207.13   $1,207.05   $1,207.20