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 $114.69   3.456%   $118.6537   $118.65   $118.65   $118.70  
  Purchase #2 $194.73   7.345%   $209.0329   $209.03   $209.05   $209.00  
  Purchase #3 $39.38   4.662%   $41.2159   $41.22   $41.20   $41.20  
  Purchase #4 $153.77   6.183%   $163.2776   $163.28   $163.30   $163.30  
  Purchase #5 $154.27   9.255%   $168.5477   $168.55   $168.55   $168.50  
  Purchase #6 $156.42   11.792%   $174.865   $174.87   $174.85   $174.90  
  Purchase #7 $129.32   8.311%   $140.0678   $140.07   $140.05   $140.10  
  7 purchase totals = $942.58       $1,015.6606   $1,015.67   $1,015.65   $1,015.70