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 $60.62   3.341%   $62.6453   $62.65   $62.65   $62.60  
  Purchase #2 $168.49   13.623%   $191.4434   $191.44   $191.45   $191.40  
  Purchase #3 $66.66   5.415%   $70.2696   $70.27   $70.25   $70.30  
  Purchase #4 $91.33   8.279%   $98.8912   $98.89   $98.90   $98.90  
  Purchase #5 $205.55   5.152%   $216.1399   $216.14   $216.15   $216.10  
  Purchase #6 $14.83   12.712%   $16.7152   $16.72   $16.70   $16.70  
  Purchase #7 $98.59   5.290%   $103.8054   $103.81   $103.80   $103.80  
  7 purchase totals = $706.07       $759.9100   $759.92   $759.90   $759.80