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 $58.25   8.778%   $63.3632   $63.36   $63.35   $63.40  
  Purchase #2 $187.61   7.194%   $201.1067   $201.11   $201.10   $201.10  
  Purchase #3 $213.40   4.270%   $222.5122   $222.51   $222.50   $222.50  
  Purchase #4 $195.37   3.722%   $202.6417   $202.64   $202.65   $202.60  
  Purchase #5 $185.64   9.712%   $203.6694   $203.67   $203.65   $203.70  
  Purchase #6 $60.59   3.311%   $62.5961   $62.60   $62.60   $62.60  
  Purchase #7 $97.67   8.782%   $106.2474   $106.25   $106.25   $106.20  
  7 purchase totals = $998.53       $1,062.1367   $1,062.14   $1,062.10   $1,062.10