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 $168.30   8.453%   $182.5264   $182.53   $182.55   $182.50  
  Purchase #2 $222.95   9.554%   $244.2506   $244.25   $244.25   $244.30  
  Purchase #3 $244.89   9.171%   $267.3489   $267.35   $267.35   $267.30  
  Purchase #4 $56.38   7.651%   $60.6936   $60.69   $60.70   $60.70  
  Purchase #5 $110.70   4.349%   $115.5143   $115.51   $115.50   $115.50  
  Purchase #6 $119.36   13.619%   $135.6156   $135.62   $135.60   $135.60  
  Purchase #7 $96.49   13.707%   $109.7159   $109.72   $109.70   $109.70  
  7 purchase totals = $1,019.07       $1,115.6653   $1,115.67   $1,115.65   $1,115.60