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 $169.69   3.684%   $175.9414   $175.94   $175.95   $175.90  
  Purchase #2 $238.30   13.153%   $269.6436   $269.64   $269.65   $269.60  
  Purchase #3 $26.97   10.520%   $29.8072   $29.81   $29.80   $29.80  
  Purchase #4 $193.97   6.193%   $205.9826   $205.98   $206.00   $206.00  
  Purchase #5 $30.31   3.761%   $31.45   $31.45   $31.45   $31.50  
  Purchase #6 $17.42   13.737%   $19.813   $19.81   $19.80   $19.80  
  Purchase #7 $32.92   5.107%   $34.6012   $34.60   $34.60   $34.60  
  7 purchase totals = $709.58       $767.2390   $767.23   $767.25   $767.20