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 $194.58   5.709%   $205.6886   $205.69   $205.70   $205.70  
  Purchase #2 $224.66   9.230%   $245.3961   $245.40   $245.40   $245.40  
  Purchase #3 $49.59   5.852%   $52.492   $52.49   $52.50   $52.50  
  Purchase #4 $127.26   8.159%   $137.6431   $137.64   $137.65   $137.60  
  Purchase #5 $169.33   11.565%   $188.913   $188.91   $188.90   $188.90  
  Purchase #6 $86.39   6.455%   $91.9665   $91.97   $91.95   $92.00  
  Purchase #7 $40.60   11.759%   $45.3742   $45.37   $45.35   $45.40  
  7 purchase totals = $892.41       $967.4735   $967.47   $967.45   $967.50