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 $107.85   3.415%   $111.5331   $111.53   $111.55   $111.50  
  Purchase #2 $248.36   5.444%   $261.8807   $261.88   $261.90   $261.90  
  Purchase #3 $199.68   4.860%   $209.3844   $209.38   $209.40   $209.40  
  Purchase #4 $201.41   5.600%   $212.689   $212.69   $212.70   $212.70  
  Purchase #5 $244.80   11.447%   $272.8223   $272.82   $272.80   $272.80  
  Purchase #6 $184.46   10.605%   $204.022   $204.02   $204.00   $204.00  
  Purchase #7 $167.94   12.518%   $188.9627   $188.96   $188.95   $189.00  
  7 purchase totals = $1,354.50       $1,461.2942   $1,461.28   $1,461.30   $1,461.30