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 $162.26   5.166%   $170.6424   $170.64   $170.65   $170.60  
  Purchase #2 $68.39   11.803%   $76.4621   $76.46   $76.45   $76.50  
  Purchase #3 $222.51   4.627%   $232.8055   $232.81   $232.80   $232.80  
  Purchase #4 $197.40   8.847%   $214.864   $214.86   $214.85   $214.90  
  Purchase #5 $46.64   3.338%   $48.1968   $48.20   $48.20   $48.20  
  Purchase #6 $238.31   8.864%   $259.4338   $259.43   $259.45   $259.40  
  Purchase #7 $53.89   12.693%   $60.7303   $60.73   $60.75   $60.70  
  7 purchase totals = $989.40       $1,063.1349   $1,063.13   $1,063.15   $1,063.10