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 $30.71   10.599%   $33.965   $33.97   $33.95   $34.00  
  Purchase #2 $222.89   13.748%   $253.5329   $253.53   $253.55   $253.50  
  Purchase #3 $106.58   7.517%   $114.5916   $114.59   $114.60   $114.60  
  Purchase #4 $191.32   5.422%   $201.6934   $201.69   $201.70   $201.70  
  Purchase #5 $237.93   11.573%   $265.4656   $265.47   $265.45   $265.50  
  Purchase #6 $163.36   7.124%   $174.9978   $175.00   $175.00   $175.00  
  Purchase #7 $135.89   10.814%   $150.5851   $150.59   $150.60   $150.60  
  7 purchase totals = $1,088.68       $1,194.8314   $1,194.84   $1,194.85   $1,194.90