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 $85.86   10.741%   $95.0822   $95.08   $95.10   $95.10  
  Purchase #2 $171.71   10.539%   $189.8065   $189.81   $189.80   $189.80  
  Purchase #3 $216.61   13.767%   $246.4307   $246.43   $246.45   $246.40  
  Purchase #4 $101.47   8.236%   $109.8271   $109.83   $109.85   $109.80  
  Purchase #5 $94.33   13.552%   $107.1136   $107.11   $107.10   $107.10  
  Purchase #6 $241.52   3.683%   $250.4152   $250.42   $250.40   $250.40  
  Purchase #7 $237.42   6.152%   $252.0261   $252.03   $252.05   $252.00  
  7 purchase totals = $1,148.92       $1,250.7014   $1,250.71   $1,250.75   $1,250.60