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 $91.76   3.755%   $95.2056   $95.21   $95.20   $95.20  
  Purchase #2 $96.95   4.740%   $101.5454   $101.55   $101.55   $101.50  
  Purchase #3 $194.99   6.610%   $207.8788   $207.88   $207.90   $207.90  
  Purchase #4 $5.79   3.511%   $5.9933   $5.99   $6.00   $6.00  
  Purchase #5 $125.38   7.693%   $135.0255   $135.03   $135.05   $135.00  
  Purchase #6 $246.26   5.381%   $259.5113   $259.51   $259.50   $259.50  
  Purchase #7 $233.61   12.276%   $262.288   $262.29   $262.30   $262.30  
  7 purchase totals = $994.74       $1,067.4479   $1,067.46   $1,067.50   $1,067.40