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 $184.59   9.403%   $201.947   $201.95   $201.95   $201.90  
  Purchase #2 $49.91   7.206%   $53.5065   $53.51   $53.50   $53.50  
  Purchase #3 $112.87   6.793%   $120.5373   $120.54   $120.55   $120.50  
  Purchase #4 $181.59   11.545%   $202.5546   $202.55   $202.55   $202.60  
  Purchase #5 $19.41   6.777%   $20.7254   $20.73   $20.75   $20.70  
  Purchase #6 $194.88   5.554%   $205.7036   $205.70   $205.70   $205.70  
  Purchase #7 $161.48   10.221%   $177.9849   $177.98   $178.00   $178.00  
  7 purchase totals = $904.73       $982.9593   $982.96   $983.00   $982.90