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 $62.39   13.423%   $70.7646   $70.76   $70.75   $70.80  
  Purchase #2 $173.83   4.208%   $181.1448   $181.14   $181.15   $181.10  
  Purchase #3 $218.54   11.606%   $243.9038   $243.90   $243.90   $243.90  
  Purchase #4 $162.72   9.495%   $178.1703   $178.17   $178.15   $178.20  
  Purchase #5 $238.64   5.161%   $250.9562   $250.96   $250.95   $251.00  
  Purchase #6 $246.36   9.487%   $269.7322   $269.73   $269.75   $269.70  
  Purchase #7 $239.68   5.231%   $252.2177   $252.22   $252.20   $252.20  
  7 purchase totals = $1,342.16       $1,446.8896   $1,446.88   $1,446.85   $1,446.90