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 $54.84   7.451%   $58.9261   $58.93   $58.95   $58.90  
  Purchase #2 $164.34   11.768%   $183.6795   $183.68   $183.70   $183.70  
  Purchase #3 $199.80   9.596%   $218.9728   $218.97   $218.95   $219.00  
  Purchase #4 $156.71   12.312%   $176.0041   $176.00   $176.00   $176.00  
  Purchase #5 $206.87   5.431%   $218.1051   $218.11   $218.10   $218.10  
  Purchase #6 $32.95   6.247%   $35.0084   $35.01   $35.00   $35.00  
  Purchase #7 $189.98   11.231%   $211.3167   $211.32   $211.30   $211.30  
  7 purchase totals = $1,005.49       $1,102.0127   $1,102.02   $1,102.00   $1,102.00