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 $84.49   13.555%   $95.9426   $95.94   $95.95   $95.90  
  Purchase #2 $52.37   7.325%   $56.2061   $56.21   $56.20   $56.20  
  Purchase #3 $57.79   4.106%   $60.1629   $60.16   $60.15   $60.20  
  Purchase #4 $183.45   11.743%   $204.9925   $204.99   $205.00   $205.00  
  Purchase #5 $247.88   9.232%   $270.7643   $270.76   $270.75   $270.80  
  Purchase #6 $145.47   5.711%   $153.7778   $153.78   $153.80   $153.80  
  Purchase #7 $16.93   10.286%   $18.6714   $18.67   $18.65   $18.70  
  7 purchase totals = $788.38       $860.5176   $860.51   $860.50   $860.60