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 $167.37   10.137%   $184.3363   $184.34   $184.35   $184.30  
  Purchase #2 $17.29   5.822%   $18.2966   $18.30   $18.30   $18.30  
  Purchase #3 $101.98   8.433%   $110.58   $110.58   $110.60   $110.60  
  Purchase #4 $250.40   6.194%   $265.9098   $265.91   $265.90   $265.90  
  Purchase #5 $82.95   3.788%   $86.0921   $86.09   $86.10   $86.10  
  Purchase #6 $243.28   8.318%   $263.516   $263.52   $263.50   $263.50  
  Purchase #7 $93.35   13.874%   $106.3014   $106.30   $106.30   $106.30  
  7 purchase totals = $956.62       $1,035.0322   $1,035.04   $1,035.05   $1,035.00