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 $193.86   8.508%   $210.3536   $210.35   $210.35   $210.40  
  Purchase #2 $45.65   8.241%   $49.412   $49.41   $49.40   $49.40  
  Purchase #3 $111.36   10.701%   $123.2766   $123.28   $123.30   $123.30  
  Purchase #4 $246.61   3.718%   $255.779   $255.78   $255.80   $255.80  
  Purchase #5 $186.99   11.652%   $208.7781   $208.78   $208.80   $208.80  
  Purchase #6 $182.55   9.508%   $199.9069   $199.91   $199.90   $199.90  
  Purchase #7 $56.29   7.789%   $60.6744   $60.67   $60.65   $60.70  
  7 purchase totals = $1,023.31       $1,108.1806   $1,108.18   $1,108.20   $1,108.30