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 $32.26   7.718%   $34.7498   $34.75   $34.75   $34.70  
  Purchase #2 $249.95   12.397%   $280.9363   $280.94   $280.95   $280.90  
  Purchase #3 $98.61   8.180%   $106.6763   $106.68   $106.70   $106.70  
  Purchase #4 $203.85   8.586%   $221.3526   $221.35   $221.35   $221.40  
  Purchase #5 $183.36   3.858%   $190.434   $190.43   $190.45   $190.40  
  Purchase #6 $143.70   13.561%   $163.1872   $163.19   $163.20   $163.20  
  Purchase #7 $60.64   6.207%   $64.4039   $64.40   $64.40   $64.40  
  7 purchase totals = $972.37       $1,061.7401   $1,061.74   $1,061.80   $1,061.70