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 $210.45   11.684%   $235.039   $235.04   $235.05   $235.00  
  Purchase #2 $209.44   10.271%   $230.9516   $230.95   $230.95   $231.00  
  Purchase #3 $94.72   10.413%   $104.5832   $104.58   $104.60   $104.60  
  Purchase #4 $178.51   8.672%   $193.9904   $193.99   $194.00   $194.00  
  Purchase #5 $139.71   5.520%   $147.422   $147.42   $147.40   $147.40  
  Purchase #6 $214.52   10.279%   $236.5705   $236.57   $236.55   $236.60  
  Purchase #7 $59.53   13.597%   $67.6243   $67.62   $67.60   $67.60  
  7 purchase totals = $1,106.88       $1,216.1810   $1,216.17   $1,216.15   $1,216.20