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 $106.87   11.320%   $118.9677   $118.97   $118.95   $119.00  
  Purchase #2 $126.94   5.248%   $133.6018   $133.60   $133.60   $133.60  
  Purchase #3 $49.27   6.185%   $52.3173   $52.32   $52.30   $52.30  
  Purchase #4 $68.69   10.693%   $76.035   $76.04   $76.05   $76.00  
  Purchase #5 $77.32   9.103%   $84.3584   $84.36   $84.35   $84.40  
  Purchase #6 $11.93   7.392%   $12.8119   $12.81   $12.80   $12.80  
  Purchase #7 $184.39   13.570%   $209.4117   $209.41   $209.40   $209.40  
  7 purchase totals = $625.41       $687.5038   $687.51   $687.45   $687.50