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 $92.97   3.214%   $95.9581   $95.96   $95.95   $96.00  
  Purchase #2 $8.51   6.401%   $9.0547   $9.05   $9.05   $9.10  
  Purchase #3 $227.29   5.535%   $239.8705   $239.87   $239.85   $239.90  
  Purchase #4 $125.39   3.832%   $130.1949   $130.19   $130.20   $130.20  
  Purchase #5 $91.92   3.241%   $94.8991   $94.90   $94.90   $94.90  
  Purchase #6 $98.64   9.139%   $107.6547   $107.65   $107.65   $107.70  
  Purchase #7 $89.56   11.270%   $99.6534   $99.65   $99.65   $99.70  
  7 purchase totals = $734.28       $777.2854   $777.27   $777.25   $777.50