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 $240.49   11.283%   $267.6245   $267.62   $267.60   $267.60  
  Purchase #2 $250.96   5.263%   $264.168   $264.17   $264.15   $264.20  
  Purchase #3 $169.58   9.534%   $185.7478   $185.75   $185.75   $185.70  
  Purchase #4 $148.33   11.199%   $164.9415   $164.94   $164.95   $164.90  
  Purchase #5 $206.86   11.603%   $230.862   $230.86   $230.85   $230.90  
  Purchase #6 $148.78   9.256%   $162.5511   $162.55   $162.55   $162.60  
  Purchase #7 $243.61   13.360%   $276.1563   $276.16   $276.15   $276.20  
  7 purchase totals = $1,408.61       $1,552.0512   $1,552.05   $1,552.00   $1,552.10