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 $86.35   11.146%   $95.9746   $95.97   $95.95   $96.00  
  Purchase #2 $105.36   7.253%   $113.0018   $113.00   $113.00   $113.00  
  Purchase #3 $157.66   8.334%   $170.7994   $170.80   $170.80   $170.80  
  Purchase #4 $11.97   3.636%   $12.4052   $12.41   $12.40   $12.40  
  Purchase #5 $177.69   6.570%   $189.3642   $189.36   $189.35   $189.40  
  Purchase #6 $239.39   11.803%   $267.6452   $267.65   $267.65   $267.60  
  Purchase #7 $192.85   4.524%   $201.5745   $201.57   $201.55   $201.60  
  7 purchase totals = $971.27       $1,050.7649   $1,050.76   $1,050.70   $1,050.80