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 $55.43   11.818%   $61.9807   $61.98   $62.00   $62.00  
  Purchase #2 $134.58   7.644%   $144.8673   $144.87   $144.85   $144.90  
  Purchase #3 $57.70   10.434%   $63.7204   $63.72   $63.70   $63.70  
  Purchase #4 $155.87   11.205%   $173.3352   $173.34   $173.35   $173.30  
  Purchase #5 $195.55   8.533%   $212.2363   $212.24   $212.25   $212.20  
  Purchase #6 $245.47   7.856%   $264.7541   $264.75   $264.75   $264.80  
  Purchase #7 $78.44   8.371%   $85.0062   $85.01   $85.00   $85.00  
  7 purchase totals = $923.04       $1,005.9002   $1,005.91   $1,005.90   $1,005.90