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 $194.47   4.833%   $203.8687   $203.87   $203.85   $203.90  
  Purchase #2 $222.58   6.207%   $236.3955   $236.40   $236.40   $236.40  
  Purchase #3 $79.80   7.661%   $85.9135   $85.91   $85.90   $85.90  
  Purchase #4 $249.35   7.207%   $267.3207   $267.32   $267.30   $267.30  
  Purchase #5 $196.85   4.376%   $205.4642   $205.46   $205.45   $205.50  
  Purchase #6 $87.90   9.836%   $96.5458   $96.55   $96.55   $96.50  
  Purchase #7 $216.66   7.823%   $233.6093   $233.61   $233.60   $233.60  
  7 purchase totals = $1,247.61       $1,329.1177   $1,329.12   $1,329.05   $1,329.10