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 $214.96   5.386%   $226.5377   $226.54   $226.55   $226.50  
  Purchase #2 $11.76   3.270%   $12.1446   $12.14   $12.15   $12.10  
  Purchase #3 $180.37   12.746%   $203.36   $203.36   $203.35   $203.40  
  Purchase #4 $196.75   7.147%   $210.8117   $210.81   $210.80   $210.80  
  Purchase #5 $154.51   13.693%   $175.6671   $175.67   $175.65   $175.70  
  Purchase #6 $161.49   3.536%   $167.2003   $167.20   $167.20   $167.20  
  Purchase #7 $60.84   8.551%   $66.0424   $66.04   $66.05   $66.00  
  7 purchase totals = $980.68       $1,061.7638   $1,061.76   $1,061.75   $1,061.70