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 $46.55   3.212%   $48.0452   $48.05   $48.05   $48.00  
  Purchase #2 $192.86   6.498%   $205.392   $205.39   $205.40   $205.40  
  Purchase #3 $20.29   6.403%   $21.5892   $21.59   $21.60   $21.60  
  Purchase #4 $243.76   10.723%   $269.8984   $269.90   $269.90   $269.90  
  Purchase #5 $249.69   6.448%   $265.79   $265.79   $265.80   $265.80  
  Purchase #6 $138.56   11.403%   $154.36   $154.36   $154.35   $154.40  
  Purchase #7 $134.77   5.401%   $142.0489   $142.05   $142.05   $142.00  
  7 purchase totals = $1,026.48       $1,107.1237   $1,107.13   $1,107.15   $1,107.10