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 $168.78   3.833%   $175.2493   $175.25   $175.25   $175.20  
  Purchase #2 $60.62   5.132%   $63.731   $63.73   $63.75   $63.70  
  Purchase #3 $169.34   10.162%   $186.5483   $186.55   $186.55   $186.50  
  Purchase #4 $180.83   11.585%   $201.7792   $201.78   $201.80   $201.80  
  Purchase #5 $155.80   6.755%   $166.3243   $166.32   $166.30   $166.30  
  Purchase #6 $217.47   13.761%   $247.396   $247.40   $247.40   $247.40  
  Purchase #7 $20.75   5.743%   $21.9417   $21.94   $21.95   $21.90  
  7 purchase totals = $973.59       $1,062.9698   $1,062.97   $1,063.00   $1,062.80