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 $242.38   8.549%   $263.1011   $263.10   $263.10   $263.10  
  Purchase #2 $107.88   4.414%   $112.6418   $112.64   $112.65   $112.60  
  Purchase #3 $187.32   10.391%   $206.7844   $206.78   $206.80   $206.80  
  Purchase #4 $231.52   13.720%   $263.2845   $263.28   $263.30   $263.30  
  Purchase #5 $231.47   12.291%   $259.92   $259.92   $259.90   $259.90  
  Purchase #6 $133.89   9.398%   $146.473   $146.47   $146.45   $146.50  
  Purchase #7 $197.90   7.104%   $211.9588   $211.96   $211.95   $212.00  
  7 purchase totals = $1,332.36       $1,464.1636   $1,464.15   $1,464.15   $1,464.20