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 $61.92   8.163%   $66.9745   $66.97   $66.95   $67.00  
  Purchase #2 $249.59   5.490%   $263.2925   $263.29   $263.30   $263.30  
  Purchase #3 $145.30   10.125%   $160.0116   $160.01   $160.00   $160.00  
  Purchase #4 $215.88   3.501%   $223.438   $223.44   $223.45   $223.40  
  Purchase #5 $21.99   11.873%   $24.6009   $24.60   $24.60   $24.60  
  Purchase #6 $78.35   7.254%   $84.0335   $84.03   $84.05   $84.00  
  Purchase #7 $242.90   8.655%   $263.923   $263.92   $263.90   $263.90  
  7 purchase totals = $1,015.93       $1,086.2740   $1,086.26   $1,086.25   $1,086.20