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 $76.96   11.401%   $85.7342   $85.73   $85.75   $85.70  
  Purchase #2 $90.95   5.381%   $95.844   $95.84   $95.85   $95.80  
  Purchase #3 $148.82   11.567%   $166.034   $166.03   $166.05   $166.00  
  Purchase #4 $145.29   13.213%   $164.4872   $164.49   $164.50   $164.50  
  Purchase #5 $185.97   6.737%   $198.4988   $198.50   $198.50   $198.50  
  Purchase #6 $130.67   8.747%   $142.0997   $142.10   $142.10   $142.10  
  Purchase #7 $150.62   7.350%   $161.6906   $161.69   $161.70   $161.70  
  7 purchase totals = $929.28       $1,014.3885   $1,014.38   $1,014.45   $1,014.30