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 $163.56   11.383%   $182.178   $182.18   $182.20   $182.20  
  Purchase #2 $14.60   4.622%   $15.2748   $15.27   $15.25   $15.30  
  Purchase #3 $11.26   4.674%   $11.7863   $11.79   $11.80   $11.80  
  Purchase #4 $192.79   13.574%   $218.9593   $218.96   $218.95   $219.00  
  Purchase #5 $207.93   8.819%   $226.2673   $226.27   $226.25   $226.30  
  Purchase #6 $190.68   6.362%   $202.8111   $202.81   $202.80   $202.80  
  Purchase #7 $197.92   6.559%   $210.9016   $210.90   $210.90   $210.90  
  7 purchase totals = $978.74       $1,068.1784   $1,068.18   $1,068.15   $1,068.30