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 $42.76   3.562%   $44.2831   $44.28   $44.30   $44.30  
  Purchase #2 $201.48   4.170%   $209.8817   $209.88   $209.90   $209.90  
  Purchase #3 $165.89   11.668%   $185.246   $185.25   $185.25   $185.20  
  Purchase #4 $244.37   11.138%   $271.5879   $271.59   $271.60   $271.60  
  Purchase #5 $202.99   5.553%   $214.262   $214.26   $214.25   $214.30  
  Purchase #6 $227.72   12.345%   $255.832   $255.83   $255.85   $255.80  
  Purchase #7 $240.33   11.546%   $268.0785   $268.08   $268.10   $268.10  
  7 purchase totals = $1,325.54       $1,449.1712   $1,449.17   $1,449.25   $1,449.20