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 $56.45   9.744%   $61.9505   $61.95   $61.95   $62.00  
  Purchase #2 $162.97   6.841%   $174.1188   $174.12   $174.10   $174.10  
  Purchase #3 $234.64   7.689%   $252.6815   $252.68   $252.70   $252.70  
  Purchase #4 $166.89   6.220%   $177.2706   $177.27   $177.25   $177.30  
  Purchase #5 $63.65   7.857%   $68.651   $68.65   $68.65   $68.70  
  Purchase #6 $227.27   9.204%   $248.1879   $248.19   $248.20   $248.20  
  Purchase #7 $174.65   7.366%   $187.5147   $187.51   $187.50   $187.50  
  7 purchase totals = $1,086.52       $1,170.3750   $1,170.37   $1,170.35   $1,170.50