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 $209.26   11.717%   $233.779   $233.78   $233.80   $233.80  
  Purchase #2 $25.99   9.132%   $28.3634   $28.36   $28.35   $28.40  
  Purchase #3 $63.80   12.527%   $71.7922   $71.79   $71.80   $71.80  
  Purchase #4 $94.83   11.520%   $105.7544   $105.75   $105.75   $105.80  
  Purchase #5 $237.57   6.543%   $253.1142   $253.11   $253.10   $253.10  
  Purchase #6 $133.57   10.700%   $147.862   $147.86   $147.85   $147.90  
  Purchase #7 $100.45   13.192%   $113.7014   $113.70   $113.70   $113.70  
  7 purchase totals = $865.47       $954.3666   $954.35   $954.35   $954.50