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 $87.47   11.411%   $97.4512   $97.45   $97.45   $97.50  
  Purchase #2 $101.76   12.135%   $114.1086   $114.11   $114.10   $114.10  
  Purchase #3 $150.59   5.348%   $158.6436   $158.64   $158.65   $158.60  
  Purchase #4 $140.83   5.224%   $148.187   $148.19   $148.20   $148.20  
  Purchase #5 $171.75   6.677%   $183.2177   $183.22   $183.20   $183.20  
  Purchase #6 $147.69   13.483%   $167.603   $167.60   $167.60   $167.60  
  Purchase #7 $5.32   8.843%   $5.7904   $5.79   $5.80   $5.80  
  7 purchase totals = $805.41       $875.0015   $875.00   $875.00   $875.00