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 $114.99   13.575%   $130.5999   $130.60   $130.60   $130.60  
  Purchase #2 $200.52   5.381%   $211.31   $211.31   $211.30   $211.30  
  Purchase #3 $59.72   8.457%   $64.7705   $64.77   $64.75   $64.80  
  Purchase #4 $30.90   11.337%   $34.4031   $34.40   $34.40   $34.40  
  Purchase #5 $236.57   13.533%   $268.585   $268.59   $268.60   $268.60  
  Purchase #6 $206.87   4.704%   $216.6012   $216.60   $216.60   $216.60  
  Purchase #7 $79.52   6.617%   $84.7818   $84.78   $84.80   $84.80  
  7 purchase totals = $929.09       $1,011.0515   $1,011.05   $1,011.05   $1,011.10