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 $155.93   4.688%   $163.24   $163.24   $163.25   $163.20  
  Purchase #2 $201.73   3.290%   $208.3669   $208.37   $208.35   $208.40  
  Purchase #3 $65.70   3.250%   $67.8353   $67.84   $67.85   $67.80  
  Purchase #4 $33.85   8.639%   $36.7743   $36.77   $36.75   $36.80  
  Purchase #5 $185.32   10.451%   $204.6878   $204.69   $204.70   $204.70  
  Purchase #6 $111.64   7.529%   $120.0454   $120.05   $120.05   $120.00  
  Purchase #7 $209.32   10.494%   $231.286   $231.29   $231.30   $231.30  
  7 purchase totals = $963.49       $1,032.2357   $1,032.25   $1,032.25   $1,032.20