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 $86.45   10.134%   $95.2108   $95.21   $95.20   $95.20  
  Purchase #2 $208.72   7.746%   $224.8875   $224.89   $224.90   $224.90  
  Purchase #3 $201.63   5.536%   $212.7922   $212.79   $212.80   $212.80  
  Purchase #4 $112.98   12.253%   $126.8234   $126.82   $126.80   $126.80  
  Purchase #5 $172.68   6.320%   $183.5934   $183.59   $183.60   $183.60  
  Purchase #6 $99.65   7.204%   $106.8288   $106.83   $106.85   $106.80  
  Purchase #7 $127.28   3.797%   $132.1128   $132.11   $132.10   $132.10  
  7 purchase totals = $1,009.39       $1,082.2489   $1,082.24   $1,082.25   $1,082.20