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 $58.54   5.270%   $61.6251   $61.63   $61.65   $61.60  
  Purchase #2 $196.53   3.195%   $202.8091   $202.81   $202.80   $202.80  
  Purchase #3 $223.80   6.500%   $238.347   $238.35   $238.35   $238.30  
  Purchase #4 $170.91   11.607%   $190.7475   $190.75   $190.75   $190.70  
  Purchase #5 $21.27   4.728%   $22.2756   $22.28   $22.30   $22.30  
  Purchase #6 $220.69   10.664%   $244.2244   $244.22   $244.20   $244.20  
  Purchase #7 $129.99   8.245%   $140.7077   $140.71   $140.70   $140.70  
  7 purchase totals = $1,021.73       $1,100.7364   $1,100.75   $1,100.75   $1,100.60