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 $194.92   6.329%   $207.2565   $207.26   $207.25   $207.30  
  Purchase #2 $107.97   3.433%   $111.6766   $111.68   $111.70   $111.70  
  Purchase #3 $13.74   11.705%   $15.3483   $15.35   $15.35   $15.30  
  Purchase #4 $181.26   9.557%   $198.583   $198.58   $198.60   $198.60  
  Purchase #5 $147.51   13.614%   $167.592   $167.59   $167.60   $167.60  
  Purchase #6 $195.86   5.289%   $206.219   $206.22   $206.20   $206.20  
  Purchase #7 $230.35   7.627%   $247.9188   $247.92   $247.90   $247.90  
  7 purchase totals = $1,071.61       $1,154.5942   $1,154.60   $1,154.60   $1,154.60