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 $193.46   8.309%   $209.5346   $209.53   $209.55   $209.50  
  Purchase #2 $57.35   13.304%   $64.9798   $64.98   $65.00   $65.00  
  Purchase #3 $242.34   10.425%   $267.6039   $267.60   $267.60   $267.60  
  Purchase #4 $218.85   5.659%   $231.2347   $231.23   $231.25   $231.20  
  Purchase #5 $60.94   3.660%   $63.1704   $63.17   $63.15   $63.20  
  Purchase #6 $189.44   8.833%   $206.1732   $206.17   $206.15   $206.20  
  Purchase #7 $18.63   10.827%   $20.6471   $20.65   $20.65   $20.60  
  7 purchase totals = $981.01       $1,063.3437   $1,063.33   $1,063.35   $1,063.30