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 $117.95   6.234%   $125.303   $125.30   $125.30   $125.30  
  Purchase #2 $124.70   8.181%   $134.9017   $134.90   $134.90   $134.90  
  Purchase #3 $183.32   3.641%   $189.9947   $189.99   $190.00   $190.00  
  Purchase #4 $87.52   13.136%   $99.0166   $99.02   $99.00   $99.00  
  Purchase #5 $96.68   7.653%   $104.0789   $104.08   $104.10   $104.10  
  Purchase #6 $245.61   9.268%   $268.3731   $268.37   $268.35   $268.40  
  Purchase #7 $83.78   13.758%   $95.3065   $95.31   $95.30   $95.30  
  7 purchase totals = $939.56       $1,016.9745   $1,016.97   $1,016.95   $1,017.00