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 $191.58   7.107%   $205.1956   $205.20   $205.20   $205.20  
  Purchase #2 $246.87   3.256%   $254.9081   $254.91   $254.90   $254.90  
  Purchase #3 $86.64   8.643%   $94.1283   $94.13   $94.15   $94.10  
  Purchase #4 $124.97   4.749%   $130.9048   $130.90   $130.90   $130.90  
  Purchase #5 $191.86   3.328%   $198.2451   $198.25   $198.25   $198.20  
  Purchase #6 $45.35   6.871%   $48.466   $48.47   $48.45   $48.50  
  Purchase #7 $162.35   3.167%   $167.4916   $167.49   $167.50   $167.50  
  7 purchase totals = $1,049.62       $1,099.3395   $1,099.35   $1,099.35   $1,099.30