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 $55.64   11.842%   $62.2289   $62.23   $62.25   $62.20  
  Purchase #2 $123.30   4.134%   $128.3972   $128.40   $128.40   $128.40  
  Purchase #3 $157.38   6.246%   $167.21   $167.21   $167.20   $167.20  
  Purchase #4 $31.28   11.174%   $34.7752   $34.78   $34.80   $34.80  
  Purchase #5 $114.74   6.562%   $122.2692   $122.27   $122.25   $122.30  
  Purchase #6 $64.51   4.563%   $67.4536   $67.45   $67.45   $67.50  
  Purchase #7 $150.34   8.548%   $163.1911   $163.19   $163.20   $163.20  
  7 purchase totals = $697.19       $745.5252   $745.53   $745.55   $745.60