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 $44.74   5.727%   $47.3023   $47.30   $47.30   $47.30  
  Purchase #2 $205.77   13.586%   $233.7259   $233.73   $233.75   $233.70  
  Purchase #3 $108.77   6.539%   $115.8825   $115.88   $115.90   $115.90  
  Purchase #4 $244.34   12.232%   $274.2277   $274.23   $274.25   $274.20  
  Purchase #5 $224.58   12.364%   $252.3471   $252.35   $252.35   $252.30  
  Purchase #6 $109.32   7.530%   $117.5518   $117.55   $117.55   $117.60  
  Purchase #7 $148.37   9.661%   $162.704   $162.70   $162.70   $162.70  
  7 purchase totals = $1,085.89       $1,203.7413   $1,203.74   $1,203.80   $1,203.70