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 $152.46   7.257%   $163.524   $163.52   $163.50   $163.50  
  Purchase #2 $232.47   13.367%   $263.5443   $263.54   $263.55   $263.50  
  Purchase #3 $175.63   10.793%   $194.5857   $194.59   $194.60   $194.60  
  Purchase #4 $154.38   9.475%   $169.0075   $169.01   $169.00   $169.00  
  Purchase #5 $147.39   6.534%   $157.0205   $157.02   $157.00   $157.00  
  Purchase #6 $114.45   10.804%   $126.8152   $126.82   $126.80   $126.80  
  Purchase #7 $224.62   7.448%   $241.3497   $241.35   $241.35   $241.30  
  7 purchase totals = $1,201.40       $1,315.8469   $1,315.85   $1,315.80   $1,315.70