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 $88.38   4.270%   $92.1538   $92.15   $92.15   $92.20  
  Purchase #2 $226.51   11.562%   $252.6991   $252.70   $252.70   $252.70  
  Purchase #3 $122.73   3.528%   $127.0599   $127.06   $127.05   $127.10  
  Purchase #4 $197.87   6.516%   $210.7632   $210.76   $210.75   $210.80  
  Purchase #5 $214.98   13.744%   $244.5269   $244.53   $244.55   $244.50  
  Purchase #6 $118.69   11.205%   $131.9892   $131.99   $132.00   $132.00  
  Purchase #7 $101.79   4.285%   $106.1517   $106.15   $106.15   $106.20  
  7 purchase totals = $1,070.95       $1,165.3438   $1,165.34   $1,165.35   $1,165.50