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 $41.68   12.667%   $46.9596   $46.96   $46.95   $47.00  
  Purchase #2 $77.76   9.541%   $85.1791   $85.18   $85.20   $85.20  
  Purchase #3 $164.69   11.634%   $183.85   $183.85   $183.85   $183.90  
  Purchase #4 $232.40   13.384%   $263.5044   $263.50   $263.50   $263.50  
  Purchase #5 $140.75   7.210%   $150.8981   $150.90   $150.90   $150.90  
  Purchase #6 $205.64   7.775%   $221.6285   $221.63   $221.65   $221.60  
  Purchase #7 $132.50   8.612%   $143.9109   $143.91   $143.90   $143.90  
  7 purchase totals = $995.42       $1,095.9306   $1,095.93   $1,095.95   $1,096.00