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 $32.95   5.245%   $34.6782   $34.68   $34.70   $34.70  
  Purchase #2 $168.29   13.496%   $191.0024   $191.00   $191.00   $191.00  
  Purchase #3 $218.76   9.359%   $239.2337   $239.23   $239.25   $239.20  
  Purchase #4 $115.28   7.288%   $123.6816   $123.68   $123.70   $123.70  
  Purchase #5 $162.80   7.330%   $174.7332   $174.73   $174.75   $174.70  
  Purchase #6 $157.34   3.154%   $162.3025   $162.30   $162.30   $162.30  
  Purchase #7 $6.74   11.183%   $7.4937   $7.49   $7.50   $7.50  
  7 purchase totals = $862.16       $933.1253   $933.11   $933.20   $933.10