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 $56.77   9.151%   $61.965   $61.97   $61.95   $62.00  
  Purchase #2 $51.99   11.240%   $57.8337   $57.83   $57.85   $57.80  
  Purchase #3 $203.25   10.568%   $224.7295   $224.73   $224.75   $224.70  
  Purchase #4 $207.68   11.140%   $230.8156   $230.82   $230.80   $230.80  
  Purchase #5 $179.66   10.770%   $199.0094   $199.01   $199.00   $199.00  
  Purchase #6 $202.43   6.478%   $215.5434   $215.54   $215.55   $215.50  
  Purchase #7 $88.81   7.128%   $95.1404   $95.14   $95.15   $95.10  
  7 purchase totals = $990.59       $1,085.0370   $1,085.04   $1,085.05   $1,084.90