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 $42.28   3.272%   $43.6634   $43.66   $43.65   $43.70  
  Purchase #2 $248.89   7.353%   $267.1909   $267.19   $267.20   $267.20  
  Purchase #3 $176.94   6.233%   $187.9687   $187.97   $187.95   $188.00  
  Purchase #4 $227.74   11.832%   $254.6862   $254.69   $254.70   $254.70  
  Purchase #5 $101.99   3.208%   $105.2618   $105.26   $105.25   $105.30  
  Purchase #6 $175.61   3.215%   $181.2559   $181.26   $181.25   $181.30  
  Purchase #7 $150.54   10.832%   $166.8465   $166.85   $166.85   $166.80  
  7 purchase totals = $1,123.99       $1,206.8734   $1,206.88   $1,206.85   $1,207.00