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 $207.41   4.774%   $217.3118   $217.31   $217.30   $217.30  
  Purchase #2 $36.47   3.328%   $37.6837   $37.68   $37.70   $37.70  
  Purchase #3 $158.32   8.694%   $172.0843   $172.08   $172.10   $172.10  
  Purchase #4 $246.59   6.299%   $262.1227   $262.12   $262.10   $262.10  
  Purchase #5 $61.29   13.473%   $69.5476   $69.55   $69.55   $69.50  
  Purchase #6 $163.67   7.271%   $175.5704   $175.57   $175.55   $175.60  
  Purchase #7 $170.53   3.462%   $176.4337   $176.43   $176.45   $176.40  
  7 purchase totals = $1,044.28       $1,110.7542   $1,110.74   $1,110.75   $1,110.70