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 $214.95   8.324%   $232.8424   $232.84   $232.85   $232.80  
  Purchase #2 $154.49   8.317%   $167.3389   $167.34   $167.35   $167.30  
  Purchase #3 $56.83   11.288%   $63.245   $63.25   $63.25   $63.20  
  Purchase #4 $170.25   8.439%   $184.6174   $184.62   $184.60   $184.60  
  Purchase #5 $184.63   12.644%   $207.9746   $207.97   $207.95   $208.00  
  Purchase #6 $81.33   5.773%   $86.0252   $86.03   $86.05   $86.00  
  Purchase #7 $228.70   5.393%   $241.0338   $241.03   $241.05   $241.00  
  7 purchase totals = $1,091.18       $1,183.0773   $1,183.08   $1,183.10   $1,182.90