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 $88.36   8.866%   $96.194   $96.19   $96.20   $96.20  
  Purchase #2 $243.39   11.565%   $271.5381   $271.54   $271.55   $271.50  
  Purchase #3 $149.54   10.479%   $165.2103   $165.21   $165.20   $165.20  
  Purchase #4 $228.28   13.382%   $258.8284   $258.83   $258.85   $258.80  
  Purchase #5 $242.88   11.659%   $271.1974   $271.20   $271.20   $271.20  
  Purchase #6 $240.97   9.532%   $263.9393   $263.94   $263.95   $263.90  
  Purchase #7 $74.58   10.564%   $82.4586   $82.46   $82.45   $82.50  
  7 purchase totals = $1,268.00       $1,409.3661   $1,409.37   $1,409.40   $1,409.30