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 $95.83   9.866%   $105.2846   $105.28   $105.30   $105.30  
  Purchase #2 $190.70   3.445%   $197.2696   $197.27   $197.25   $197.30  
  Purchase #3 $209.71   8.179%   $226.8622   $226.86   $226.85   $226.90  
  Purchase #4 $34.77   7.147%   $37.255   $37.26   $37.25   $37.30  
  Purchase #5 $190.60   6.368%   $202.7374   $202.74   $202.75   $202.70  
  Purchase #6 $236.87   3.393%   $244.907   $244.91   $244.90   $244.90  
  Purchase #7 $104.96   5.349%   $110.5743   $110.57   $110.55   $110.60  
  7 purchase totals = $1,063.44       $1,124.8901   $1,124.89   $1,124.85   $1,125.00