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 $105.87   11.767%   $118.3277   $118.33   $118.35   $118.30  
  Purchase #2 $190.61   9.297%   $208.331   $208.33   $208.35   $208.30  
  Purchase #3 $211.83   7.492%   $227.7003   $227.70   $227.70   $227.70  
  Purchase #4 $161.43   9.200%   $176.2816   $176.28   $176.30   $176.30  
  Purchase #5 $77.92   9.432%   $85.2694   $85.27   $85.25   $85.30  
  Purchase #6 $83.90   3.376%   $86.7325   $86.73   $86.75   $86.70  
  Purchase #7 $194.98   4.388%   $203.5357   $203.54   $203.55   $203.50  
  7 purchase totals = $1,026.54       $1,106.1782   $1,106.18   $1,106.25   $1,106.10