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 $35.33   4.857%   $37.046   $37.05   $37.05   $37.00  
  Purchase #2 $120.33   4.518%   $125.7665   $125.77   $125.75   $125.80  
  Purchase #3 $32.82   3.871%   $34.0905   $34.09   $34.10   $34.10  
  Purchase #4 $28.60   11.245%   $31.8161   $31.82   $31.80   $31.80  
  Purchase #5 $187.88   9.239%   $205.2382   $205.24   $205.25   $205.20  
  Purchase #6 $168.62   11.523%   $188.0501   $188.05   $188.05   $188.10  
  Purchase #7 $232.49   10.106%   $255.9854   $255.99   $256.00   $256.00  
  7 purchase totals = $806.07       $877.9928   $878.01   $878.00   $878.00