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 $164.56   10.761%   $182.2683   $182.27   $182.25   $182.30  
  Purchase #2 $208.64   10.622%   $230.8017   $230.80   $230.80   $230.80  
  Purchase #3 $156.67   6.692%   $167.1544   $167.15   $167.15   $167.20  
  Purchase #4 $42.95   8.827%   $46.7412   $46.74   $46.75   $46.70  
  Purchase #5 $150.25   3.146%   $154.9769   $154.98   $155.00   $155.00  
  Purchase #6 $179.44   10.670%   $198.5862   $198.59   $198.60   $198.60  
  Purchase #7 $113.46   6.469%   $120.7997   $120.80   $120.80   $120.80  
  7 purchase totals = $1,015.97       $1,101.3284   $1,101.33   $1,101.35   $1,101.40