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 $173.86   12.579%   $195.7298   $195.73   $195.75   $195.70  
  Purchase #2 $143.97   7.849%   $155.2702   $155.27   $155.25   $155.30  
  Purchase #3 $179.62   9.814%   $197.2479   $197.25   $197.25   $197.20  
  Purchase #4 $111.49   6.696%   $118.9554   $118.96   $118.95   $119.00  
  Purchase #5 $233.41   13.386%   $264.6543   $264.65   $264.65   $264.70  
  Purchase #6 $148.69   10.854%   $164.8288   $164.83   $164.85   $164.80  
  Purchase #7 $55.91   8.453%   $60.6361   $60.64   $60.65   $60.60  
  7 purchase totals = $1,046.95       $1,157.3225   $1,157.33   $1,157.35   $1,157.30