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 $211.55   7.283%   $226.9572   $226.96   $226.95   $227.00  
  Purchase #2 $230.81   6.322%   $245.4018   $245.40   $245.40   $245.40  
  Purchase #3 $55.59   10.274%   $61.3013   $61.30   $61.30   $61.30  
  Purchase #4 $201.43   4.328%   $210.1479   $210.15   $210.15   $210.10  
  Purchase #5 $59.51   4.866%   $62.4058   $62.41   $62.40   $62.40  
  Purchase #6 $204.93   12.285%   $230.1057   $230.11   $230.10   $230.10  
  Purchase #7 $110.66   11.847%   $123.7699   $123.77   $123.75   $123.80  
  7 purchase totals = $1,074.48       $1,160.0896   $1,160.10   $1,160.05   $1,160.10