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 $85.26   10.629%   $94.3223   $94.32   $94.30   $94.30  
  Purchase #2 $83.55   13.455%   $94.7917   $94.79   $94.80   $94.80  
  Purchase #3 $22.55   3.739%   $23.3931   $23.39   $23.40   $23.40  
  Purchase #4 $62.58   8.565%   $67.94   $67.94   $67.95   $67.90  
  Purchase #5 $7.46   7.420%   $8.0135   $8.01   $8.00   $8.00  
  Purchase #6 $15.81   4.777%   $16.5652   $16.57   $16.55   $16.60  
  Purchase #7 $171.29   3.322%   $176.9803   $176.98   $177.00   $177.00  
  7 purchase totals = $448.50       $482.0061   $482.00   $482.00   $482.00