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 $43.50   10.266%   $47.9657   $47.97   $47.95   $48.00  
  Purchase #2 $177.90   5.111%   $186.9925   $186.99   $187.00   $187.00  
  Purchase #3 $84.80   13.826%   $96.5244   $96.52   $96.50   $96.50  
  Purchase #4 $223.29   6.180%   $237.0893   $237.09   $237.10   $237.10  
  Purchase #5 $233.45   11.842%   $261.0951   $261.10   $261.10   $261.10  
  Purchase #6 $47.67   13.401%   $54.0583   $54.06   $54.05   $54.10  
  Purchase #7 $107.81   6.282%   $114.5826   $114.58   $114.60   $114.60  
  7 purchase totals = $918.42       $998.3079   $998.31   $998.30   $998.40