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 $53.79   13.447%   $61.0231   $61.02   $61.00   $61.00  
  Purchase #2 $30.55   8.370%   $33.107   $33.11   $33.10   $33.10  
  Purchase #3 $43.80   8.697%   $47.6093   $47.61   $47.60   $47.60  
  Purchase #4 $177.72   3.547%   $184.0237   $184.02   $184.00   $184.00  
  Purchase #5 $250.25   11.176%   $278.2179   $278.22   $278.20   $278.20  
  Purchase #6 $184.98   10.151%   $203.7573   $203.76   $203.75   $203.80  
  Purchase #7 $191.43   9.833%   $210.2533   $210.25   $210.25   $210.30  
  7 purchase totals = $932.52       $1,017.9916   $1,017.99   $1,017.90   $1,018.00