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 $61.44   10.732%   $68.0337   $68.03   $68.05   $68.00  
  Purchase #2 $156.25   5.746%   $165.2281   $165.23   $165.25   $165.20  
  Purchase #3 $130.46   5.621%   $137.7932   $137.79   $137.80   $137.80  
  Purchase #4 $228.33   4.817%   $239.3287   $239.33   $239.35   $239.30  
  Purchase #5 $194.62   7.309%   $208.8448   $208.84   $208.85   $208.80  
  Purchase #6 $191.40   7.501%   $205.7569   $205.76   $205.75   $205.80  
  Purchase #7 $144.38   4.701%   $151.1673   $151.17   $151.15   $151.20  
  7 purchase totals = $1,106.88       $1,176.1527   $1,176.15   $1,176.20   $1,176.10