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 $182.85   13.245%   $207.0685   $207.07   $207.05   $207.10  
  Purchase #2 $160.68   4.172%   $167.3836   $167.38   $167.40   $167.40  
  Purchase #3 $73.35   12.810%   $82.7461   $82.75   $82.75   $82.70  
  Purchase #4 $211.93   7.795%   $228.4499   $228.45   $228.45   $228.40  
  Purchase #5 $181.73   5.167%   $191.12   $191.12   $191.10   $191.10  
  Purchase #6 $119.28   4.555%   $124.7132   $124.71   $124.70   $124.70  
  Purchase #7 $148.85   11.416%   $165.8427   $165.84   $165.85   $165.80  
  7 purchase totals = $1,078.67       $1,167.3240   $1,167.32   $1,167.30   $1,167.20